Enhanced eye tracking for augmented or virtual reality display systems

ABSTRACT

Described herein are methods and display systems for enhanced eye tracking for display systems, such as augmented or virtual reality display systems. The display systems may include: a light source configured to output light and a moveable diffractive grating configured to reflect light from the light source, the reflected light forming a light pattern on the eye of the user; a plurality of light detectors to detect light reflected from the eye; and one or more processors. The display system changes the orientation of the diffractive grating, such that the light pattern reflected from the diffractive grating is scanned along an axis across the eye. Light intensity patterns are obtained via the light detectors, with a light intensity pattern representing a light detector signal obtained by detecting light reflected off of the eye as the light pattern is scanned across the eye. Due to differences in how light reflects off of different parts of the eye, different eye poses provide different light intensity patterns and the eye pose is determined based on detected light intensity pattern.

PRIORITY CLAIM

This application claims priority to U.S. Patent Prov. App. 62/940,785,entitled “ENHANCED EYE TRACKING FOR AUGMENTED OR VIRTUAL REALITY DISPLAYSYSTEMS,” filed Nov. 26, 2019.

INCORPORATION BY REFERENCE

This application incorporates by reference the entirety of U.S.application Ser. No. 15/469,369 filed on Mar. 24, 2017, published onSep. 28, 2017 as U.S. Patent Application Publication No. 2017/0276948.

BACKGROUND Field

The present disclosure relates to display systems and, moreparticularly, to augmented and virtual reality display systems.

Description of the Related Art

Modern computing and display technologies have facilitated thedevelopment of systems for so called “virtual reality” or “augmentedreality” experiences, in which digitally reproduced images or portionsthereof are presented to a user in a manner wherein they seem to be, ormay be perceived as, real. A virtual reality, or “VR”, scenariotypically involves the presentation of digital or virtual imageinformation without transparency to other actual real-world visualinput; an augmented reality, or “AR”, scenario typically involvespresentation of digital or virtual image information as an augmentationto visualization of the actual world around the user. A mixed reality,or “MR”, scenario is a type of AR scenario and typically involvesvirtual objects that are integrated into, and responsive to, the naturalworld. For example, an MR scenario may include AR image content thatappears to be blocked by or is otherwise perceived to interact withobjects in the real world.

Referring to FIG. 1, an augmented reality scene 10 is depicted. The userof an AR technology sees a real-world park-like setting 20 featuringpeople, trees, buildings in the background, and a concrete platform 30.The user also perceives that he/she “sees” “virtual content” such as arobot statue 40 standing upon the real-world platform 30, and a flyingcartoon-like avatar character 50 which seems to be a personification ofa bumble bee. These elements 50, 40 are “virtual” in that they do notexist in the real world. Because the human visual perception system iscomplex, it is challenging to produce AR technology that facilitates acomfortable, natural-feeling, rich presentation of virtual imageelements amongst other virtual or real-world imagery elements.

Systems and methods disclosed herein address various challenges relatedto display technology, including AR and VR technology.

SUMMARY

In some embodiments, a display system configured to present virtualcontent to a user is provided. The display system comprises a lightsource configured to output light, a movable reflector configured toreflect the outputted light to the eye of the user to scan a patternformed of the light across the eye, a plurality of light detectorsconfigured to detect reflections of the light scanned across the eye,and one or more processors configured to perform operations. Theoperations comprise causing adjustment of the orientation of themoveable reflector, such that the reflected light is scanned across theeye. Respective light intensity patterns are obtained via the lightdetectors, wherein a light intensity pattern represents light detectorsignals at different times and the light detector signals are obtainedduring scanning of the reflected light across the eye. An eye pose ofthe eye is determined based on the light intensity patterns, the eyepose representing an orientation of the eye.

In some embodiments, a method implemented by a display system of one ormore processors is provided. The display system is configured to presentvirtual content to a user based, at least in part, on an eye pose of aneye of the user. The method comprises adjusting a position of a lightpattern directed onto the eye, such that the light pattern moves acrossthe eye. A plurality of light intensity patterns are obtained, the lightintensity patterns representing light detector signals at differenttimes, the light detector signals obtained from respective lightdetectors during adjustment of the position of the light pattern. Theeye pose of the eye is determined based on the light intensity patterns,the eye pose representing an orientation of the eye.

In some embodiments, non-transitory computer storage media is provided.The non-transitory computer storage media storing instructions that whenexecuted by a display system of one or more processors, cause the one ormore processors to perform operations. The operations comprise adjustinga position of a light pattern directed onto the eye, such that the lightpattern moves across the eye. A plurality of light intensity patternsare obtained, the light intensity patterns representing light detectorsignals at different times, the light detector signals obtained fromrespective light detectors during adjustment of the position of thelight pattern. The eye pose of the eye is determined based on the lightintensity patterns, the eye pose representing an orientation of the eye.

In some embodiments, a display system configured to present virtualcontent to a user is provided. The display system comprises a lightsource configured to output light, a movable reflector configured toreflect the outputted light to the eye of the user to scan a patternformed of the light across the eye, a plurality of light detectorsconfigured to detect reflections of the light scanned across the eye,and one or more processors configured to perform operations. Theoperations comprise obtaining, via the light detectors, respective lightintensity patterns, wherein a light intensity pattern represents lightdetector signals at different times, the light detector signals obtainedduring scanning of the reflected light across the eye. One or both of asize and position of a physiological feature of the eye is determinedbased on the light intensity patterns.

Additional examples of embodiments are provided below.

Example 1. A display system configured to present virtual content to auser, the display system comprising:

-   -   a light source configured to output light;    -   a movable reflector configured to reflect the outputted light to        the eye of the user to scan a pattern formed of the light across        the eye;    -   a plurality of light detectors configured to detect reflections        of the light scanned across the eye; and    -   one or more processors configured to perform operations        comprising:        -   causing adjustment of the orientation of the moveable            reflector, such that the reflected light is scanned across            the eye;        -   obtaining, via the light detectors, respective light            intensity patterns, wherein a light intensity pattern            represents light detector signals at different times, the            light detector signals being obtained during scanning of the            reflected light across the eye; and        -   determining, based on the light intensity patterns, an eye            pose of the eye, the eye pose representing an orientation of            the eye.

Example 2. The display system of example 1, wherein the light source isa diode.

Example 3. The display system of example 2, wherein the diode is avertical-cavity surface-emitting laser.

Example 4. The display system of example 1, wherein the movablereflector comprises a diffractive grating, wherein the diffractivegrating is configured to convert an incident beam of light from thelight source into a light pattern comprising multiple lines of lightspanning an area of the eye.

Example 5. The display system of example 1, wherein the movablereflector comprises a diffractive grating, wherein the diffractivegrating is configured to convert an incident beam of light from thelight source into a light pattern comprising multiple beams of light.

Example 6. The display system of example 1, wherein the movablereflector comprises a plurality of diffractive gratings, eachdiffractive grating configured to form a different light pattern forscanning across the eye.

Example 7. The display system of example 1, wherein the movablereflector is a microelectromechanical systems (MEMS) mirror.

Example 8. The display system of example 1, wherein the light detectorsare photodiodes, and wherein each light intensity pattern represents aplot of electrical current versus position information associated with aposition of the movable reflector.

Example 9. The display system of example 8, wherein the diffractivegrating is positioned on, or forms part of, a MEMS mirror, and whereinthe position information indicates an orientation of the MEMS mirror,the MEMS mirror being adjustable by the display system.

Example 10. The display system of example 1, wherein the light source isone of two light sources configured to output light to the movablereflector, wherein each of the light sources is configured to form arespective portion of the light pattern.

Example 11. The display system of example 1, wherein the light detectorsare photodiodes, and wherein each light intensity pattern represents aplot of electrical current versus time.

Example 12. The display system of example 1, wherein the light patterndefines a V-shape extending from a lower portion of the eye to an upperportion of the eye.

Example 13. The display system of example 1, wherein the light formingthe light pattern comprises polychromatic light.

Example 14. The display system of example 13, wherein the light patternincludes two portions extending in different directions.

Example 15. The display system of example 14, wherein each of the twoportions is formed by light of different colors.

Example 16. The display system of example 14, wherein the two portionsare configured to extend across a vertical axis of the eye, wherein thetwo portions extend in opposite directions along a horizontal axis toform a V-shape.

Example 17. The display system of example 1, wherein the light patterncomprises a plurality of sequential rows of light.

Example 18. The display system of example 17, wherein different rows oflight comprise beams of light having different amounts of divergence.

Example 19. The display system of example 18, wherein a row of lightcomprises converging beams of light, wherein an other of the rows oflight comprise collimated beams of light.

Example 20. The display system of example 18, wherein a row of lightcomprises diverging beams of light.

Example 21. The display system of example 17, wherein the rows of lightdefine an angle of less than 90° relative to a horizontal axis of theeye.

Example 22. The display system of example 1, wherein positions of thelight detectors define corners of a rectangle about the eye.

Example 23. The display system of example 1, wherein the light detectorsdefine a linear array of light detectors.

Example 24. The display system of example 1, wherein the operationsfurther comprise causing continuous scanning of the light pattern on anaxis between a first portion of the eye and a second portion of the eye.

Example 25. The display system of example 24, wherein the axis is ahorizontal axis of the eye, such that the first portion is a left orright-most portion of the eye and the second portion is the other of theleft or right-most portion of the eye.

Example 26. The display system of example 1, wherein determining the eyepose comprises:

-   -   applying a machine learning model via computing a forward pass        of the light intensity patterns, wherein an output of the        machine learning model indicates an eye pose.

Example 27. The display system of example 1, wherein determining the eyepose comprises:

-   -   accessing information identifying stored light intensity        patterns, the stored light intensity patterns being associated        with respective eye poses;    -   comparing the obtained light intensity patterns with the stored        light intensity patterns; and    -   identifying the eye pose based on the comparing.

Example 28. The display system of example 26, wherein the lightdetectors are photodiodes, wherein comparing the obtained lightintensity patterns with the stored light intensity patterns is based oncomparing positions of peaks and/or valleys of electrical current, andwherein the positions are indicative of locations of the optical patternon the eye.

Example 29. The display system of example 1, wherein the operationsfurther comprise:

-   -   determining an interpupillary distance of the user;    -   determining, based upon the determined interpupillary distance,        a scan distance across the eye to scan the light pattern; and    -   scanning the light pattern the scan distance across the eye.

Example 30. The display system of example 1, wherein the operationsfurther comprise detecting, based on the light intensity patterns, oneor both of an iris and pupil of the eye.

Example 31. The display system of example 30, wherein detecting one orboth of the iris and pupil of the eye comprises determining a size ofone or both of the iris and pupil of the eye.

Example 32. The display system of example 30, wherein detecting one orboth of the iris and pupil of the eye comprises determining a positionof one or both of the iris and pupil of the eye.

Example 33. The display system of example 1, wherein the operationsfurther comprise determining a saccadic velocity of the eye.

Example 34. The display system of example 1, further comprising awaveguide comprising out-coupling optical elements configured to outputlight to an eye of the user to form the virtual content.

Example 35. The display system of example 29, wherein the waveguide isone of a stack of waveguides, wherein some waveguides of the stack haveout-coupling optical elements configured to output light with differentamounts of wavefront divergence than out-coupling optical element ofother waveguides of the stack, wherein the different amounts ofwavefront divergence correspond to different depth planes.

Example 36. A method implemented by a display system of one or moreprocessors, the display system being configured to present virtualcontent to a user based, at least in part, on an eye pose of an eye ofthe user, wherein the method comprises:

-   -   adjusting a position of a light pattern directed onto the eye,        such that the light pattern moves across the eye;    -   obtaining a plurality of light intensity patterns, the light        intensity patterns representing light detector signals at        different times, the light detector signals obtained from        respective light detectors during adjustment of the position of        the light pattern; and    -   determining, based on the light intensity patterns, the eye pose        of the eye, the eye pose representing an orientation of the eye.

Example 37. The method of example 36, wherein adjusting the position ofthe light pattern comprises moving a moveable mirror such that the lightpattern is moved from a first portion of the eye to a second portion ofthe eye along an axis.

Example 38. The method of example 37, wherein the movable reflectorcomprises a diffractive grating, wherein the diffractive grating isconfigured to convert an incident beam of light from the light sourceinto a light pattern comprising multiple beams of light.

Example 39. The method of example 37, wherein moving the moveable mirrorcomprises rotating a microelectromechanical systems (MEMS) mirror onwhich the diffraction grating is positioned.

Example 40. The method of example 37, wherein the first portionrepresents an extremity of the iris and the second portion represents anopposite extremity of the iris along the axis.

Example 41. The method of example 37, wherein the axis is a horizontalaxis.

Example 42. The method of example 36, wherein the light pattern extendsalong a vertical axis from a lower portion of the eye to an upperportion of the eye.

Example 43. The method of example 42, wherein the light patterncomprises two portions, each portion extending along a vertical axis,and wherein the two portions extend in opposite directions along ahorizontal direction to form a V-shape.

Example 44. The method of example 36, wherein determining eye posecomprises:

-   -   applying a machine learning model via computing a forward pass        of the light intensity patterns, wherein an output of the        machine learning model indicates an eye pose.

Example 45. The method of example 36, wherein determining eye posecomprises:

-   -   accessing information identifying stored light intensity        patterns, the stored light intensity patterns being associated        with respective eye poses;    -   comparing the obtained light intensity patterns with the stored        light intensity patterns; and    -   identifying the eye pose based on the comparing.

Example 46. The method of example 45, wherein comparing the obtainedlight intensity patterns with the stored light intensity patterns isbased on comparing positions of peaks and/or valleys in the lightintensity patterns.

Example 47. Non-transitory computer storage media storing instructionsthat when executed by a display system of one or more processors, causethe one or more processors to perform operations comprising:

-   -   adjusting a position of a light pattern directed onto an eye of        a user, such that the light pattern moves across the eye;    -   obtaining a plurality of light intensity patterns, the light        intensity patterns representing light detector signals at        different times, the light detector signals obtained from        respective light detectors during adjustment of the position of        the light pattern; and    -   determining, based on the light intensity patterns, an eye pose        of the eye, the eye pose representing an orientation of the eye.

Example 48. The computer storage media of example 47, wherein theoperations further comprise:

-   -   causing projection of the light pattern to the eye via a        reflector having a diffractive grating.

Example 49. The computer storage media of example 48, wherein theorientation of the diffractive grating is adjusted such that the lightpattern is moved from a first portion of the eye to a second portion ofthe eye.

Example 50. The computer storage media of example 49, wherein the firstportion represents an extremity of the iris and the second portionrepresents an opposite extremity of the iris.

Example 51. The computer storage media of example 47, wherein the lightpattern extends from a lower portion of the eye to an upper portion ofthe eye along a vertical axis.

Example 52. The computer storage media of example 51, wherein the lightportion comprises two portions, each portion extending across the eyealong a vertical axis, and wherein the two portions extend in oppositedirections along a horizontal axis.

Example 53. The computer storage media of example 47, wherein theadjusting an orientation of the diffraction grating comprisescontrolling rotation of a microelectromechanical systems (MEMS) mirroron which the diffraction grating is positioned.

Example 54. The computer storage media of example 47, whereindetermining eye pose comprises:

-   -   applying a machine learning model via computing a forward pass        of the light intensity patterns, wherein an output of the        machine learning model indicates an eye pose.

Example 55. The computer storage media of example 47, whereindetermining eye pose comprises:

-   -   accessing information identifying stored light intensity        patterns, the stored light intensity patterns being associated        with respective eye poses;    -   comparing the obtained light intensity patterns with the stored        light intensity patterns; and    -   identifying the eye pose based on the comparing.

Example 56. The computer storage media of example 55, wherein comparingthe obtaining light intensity patterns with the stored light intensitypatterns is based on comparing positions of peaks and/or valleys.

Example 57. A display system configured to present virtual content to auser, the display system comprising:

-   -   a light source configured to output light;    -   a movable reflector configured to reflect the outputted light to        the eye of the user to scan a pattern formed of the light across        the eye;    -   a plurality of light detectors configured to detect reflections        of the light scanned across the eye; and    -   one or more processors configured to perform operations        comprising:    -   obtaining, via the light detectors, respective light intensity        patterns, wherein a light intensity pattern represents light        detector signals at different times, the light detector signals        obtained during scanning of the reflected light across the eye;        and    -   determining, based on the light intensity patterns, one or both        of a size and position of a physiological feature of the eye.

Example 58. The display system of example 57, wherein the physiologicalfeature is a pupil of the eye.

Example 59. The display system of example 58, wherein the operationsfurther comprise:

-   -   determining a first interface between an iris and the pupil of        the eye based on the light intensity patterns.

Example 60. The display system of example 59, wherein determining thefirst interface is based on positions of peaks and/or valleys in thelight intensity patterns.

Example 61. The display system of example 59, wherein the operationsfurther comprise:

-   -   determining a second interface between the iris and the pupil of        the eye based on the light intensity patterns.

Example 62. The display system of example 61, wherein the size of thepupil is determined based on the first interface and the secondinterface.

Example 63. The display system of example 61, wherein the physiologicalfeature is the pupil, and wherein the position of the pupil isdetermined based on a center of the pupil, the center being identifiedbased on the first interface and the second interface.

Example 64. The display system of example 57, wherein the physiologicalfeature is an interface between an iris and a pupil of the eye, andwherein the display system determines the position of the interface.

Example 65. A method implemented by a display system of one or moreprocessors, the display system being configured to present virtualcontent to a user based, at least in part, on an eye pose of an eye ofthe user, wherein the method comprises:

-   -   adjusting a position of a light pattern directed onto the eye,        such that the light pattern moves across the eye;    -   obtaining a plurality of light intensity patterns, the light        intensity patterns representing light detector signals at        different times, the light detector signals obtained from        respective light detectors during adjustment of the position of        the light pattern; and    -   determining, based on the light intensity patterns, a size        and/or position of a physiological feature of the eye.

Example 66. The method of example 65, wherein the physiological featureis a pupil of the eye.

Example 67. The method of example 66, further comprising:

-   -   determining a first interface between an iris and a pupil of the        eye based on the light intensity patterns.

Example 68. The method of example 67, wherein determining the firstinterface is based on positions of peaks and/or valleys in the lightintensity patterns.

Example 69. The method of example 68, further comprising:

-   -   determining a second interface between the iris and the pupil of        the eye based on the light intensity patterns.

Example 70. The method of example 69, wherein the physiological featureis the pupil, and wherein the size of the pupil is based on the firstinterface and the second interface.

Example 71. The method of example 69, wherein the physiological featureis the pupil, and wherein the position of the pupil is based on a centerof the pupil, the center being identified based on the first interfaceand the second interface.

Example 72. The method of example 65, wherein the physiological featureis an interface between an iris and a pupil of the eye, and wherein thedisplay system determines the position of the interface.

Example 73. Non-transitory computer storage media storing instructionsthat when executed by a display system of one or more processors, causethe one or more processors to perform operations comprising:

-   -   adjusting a position of a light pattern directed onto an eye of        a user, such that the light pattern moves across the eye;    -   obtaining a plurality of light intensity patterns, the light        intensity patterns representing light detector signals at        different times, the light detector signals obtained from        respective light detectors during adjustment of the position of        the light pattern; and    -   determining, based on the light intensity patterns, a size        and/or position of a physiological feature of the eye.

Example 74. The computer storage media of example 73, wherein theoperations further comprise:

-   -   determining a first interface between an iris and a pupil of the        eye based on the light intensity patterns.

Example 75. The computer storage media of example 74, whereindetermining the interface is based on positions of peaks and/or valleysin the light intensity patterns.

Example 76. The computer storage media of example 74, wherein theoperations further comprise:

-   -   determining a second interface between the iris and the pupil of        the eye based on the light intensity patterns.

Example 77. The computer storage media of example 76, wherein thephysiological feature is the pupil, and wherein the size of the pupil isdetermined based on the first interface and the second interface.

Example 78. The computer storage media of example 76, wherein thephysiological feature is the pupil, and wherein the position of thepupil is based on a center of the pupil, the center being identifiedbased on the first interface and the second interface.

Example 79. The computer storage media of example 73, wherein thephysiological feature is an interface between an iris and a pupil of theeye, and wherein the display system determines the position of theinterface.

Example 80. A display system configured to present virtual content to auser, the display system comprising:

-   -   a light source configured to output light;    -   a movable reflector configured to reflect the outputted light to        the eye of the user to scan a pattern formed of the light across        the eye;    -   a plurality of light detectors configured to detect reflections        of the light scanned across the eye; and    -   one or more processors configured to perform operations        comprising:        -   obtaining, via the light detectors, respective light            intensity patterns, wherein a light intensity pattern            represents light detector signals at different times, the            light detector signals obtained during scanning of the            reflected light across the eye; and        -   determining, based on the light intensity patterns, a speed            of rotation of the eye.

Example 81. The display system of example 80, wherein determining thespeed of rotation of the eye comprises determining a saccadic velocityof the eye.

Example 82. The display system of example 81, wherein the operationsfurther comprise predicting a pose of the eye based upon the saccadicvelocity.

Example 83. A method implemented by a display system of one or moreprocessors, the display system being configured to present virtualcontent to a user based, at least in part, on an eye pose of an eye ofthe user, wherein the method comprises:

-   -   adjusting a position of a light pattern directed onto the eye,        such that the light pattern moves across the eye;    -   obtaining a plurality of light intensity patterns, the light        intensity patterns representing light detector signals at        different times, the light detector signals obtained from        respective light detectors during adjustment of the position of        the light pattern; and    -   determining, based on the light intensity patterns, a speed of        rotation of the eye.

Example 84. Non-transitory computer storage media storing instructionsthat when executed by a display system of one or more processors, causethe one or more processors to perform operations comprising:

-   -   adjusting a position of a light pattern directed onto an eye of        a user, such that the light pattern moves across the eye;    -   obtaining a plurality of light intensity patterns, the light        intensity patterns representing light detector signals at        different times, the light detector signals obtained from        respective light detectors during adjustment of the position of        the light pattern; and    -   determining, based on the light intensity patterns, a speed of        rotation of the eye.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a user's view of an augmented reality (AR) scenethrough an AR device.

FIG. 2 illustrates a conventional display system for simulatingthree-dimensional imagery for a user.

FIGS. 3A-3C illustrate relationships between radius of curvature andfocal radius.

FIG. 4A illustrates a representation of the accommodation-vergenceresponse of the human visual system.

FIG. 4B illustrates examples of different accommodative states andvergence states of a pair of eyes of the user.

FIG. 4C illustrates an example of a representation of a top-down view ofa user viewing content via a display system.

FIG. 4D illustrates another example of a representation of a top-downview of a user viewing content via a display system.

FIG. 5 illustrates aspects of an approach for simulatingthree-dimensional imagery by modifying wavefront divergence.

FIG. 6 illustrates an example of a waveguide stack for outputting imageinformation to a user.

FIG. 7 illustrates an example of exit beams outputted by a waveguide.

FIG. 8 illustrates an example of a stacked waveguide assembly in whicheach depth plane includes images formed using multiple differentcomponent colors.

FIG. 9A illustrates a cross-sectional side view of an example of a setof stacked waveguides that each includes an in-coupling optical element.

FIG. 9B illustrates a perspective view of an example of the plurality ofstacked waveguides of FIG. 9A.

FIG. 9C illustrates a top-down plan view of an example of the pluralityof stacked waveguides of FIGS. 9A and 9B.

FIG. 9D illustrates an example of wearable display system.

FIG. 10A illustrates a plan view of a system and technique fordetermining eye pose of a user.

FIG. 10B illustrates an example reflected light intensity patternassociated with scanning the user's eye with a light pattern.

FIG. 11 illustrates an example positioning of light detectors within adisplay system for determining eye pose.

FIG. 12 illustrates an example flowchart of a process for determiningeye pose of a user's eye.

FIGS. 13A-13C illustrate an example of a light pattern being projectedonto and scanned across a user's eye.

FIGS. 14A-14C illustrate another example of a light pattern beingprojected onto and scanned across a user's eye, with the user's eye in adifferent pose than the eye shown in FIGS. 13A-13C.

FIG. 15 illustrates an example of a light pattern for scanning acrossthe user's eye.

FIG. 16 illustrates another example of a light pattern for scanningacross the user's eye.

FIGS. 17A-17C illustrate the use of two light sources for generatinglight patterns for determining eye pose of a user.

FIG. 18A illustrates an example flowchart of a process for determiningphysiological information associated with an eye.

FIGS. 18B-D illustrate an example of determining size and/or positioninformation associated with one or more physiological features.

DETAILED DESCRIPTION

AR and/or VR systems may display virtual content to a user, or viewer.

For example, this content may be displayed on a head-mounted display,e.g., as part of eyewear, that projects image information to the user'seyes. In addition, where the system is an AR system, the display mayalso transmit light from the surrounding environment to the user's eyes,to allow a view of that surrounding environment. As used herein, it willbe appreciated that a “head-mounted” or “head mountable” display is adisplay that may be mounted on the head of a viewer or user. Suchdisplays may be understood to form parts of a display system.

To provide for visually realistic virtual content, it is advantageousfor a display system to accurately track (e.g., monitor) a user's eyes.For example, an accurate determination as to an orientation of each eye(referred to herein as an eye pose) may enhance realism of presentedvirtual content. Indeed, a virtual scene (e.g., the augmented realityscene 10 illustrated in FIG. 1) may be rendered by a display systembased on a user's eyes being assigned as “render cameras” for the scene.For example, a center of the user's eyes may be assigned as rendercameras. Thus, locations of virtual content within the virtual scene maybe tied to the center of the user's eyes, along with the gaze directionand vergence of their eyes. As the user moves his/her eyes, for exampleto view virtual content or real-world content, the display system mayadjust virtual content accordingly. Thus, enhanced techniques fortracking the user's eyes may substantively enhance functionality of suchdisplay systems and provide a better viewing experience for the user.

Tracking a user's eyes may include determining vergence, gaze direction,respective centers of the user's eyeballs, and so on. At least some ofthese determinations may be effectuated based on an identification ofrespective eye poses for the user's eyes. For example, based on an eye'sorientation, the display system may determine an axis (e.g., opticaland/or visual axis) extending from the eye. This axis may represent agaze direction of the user's eye. Using eye poses for both of the user'seyes, the display system may identify locations in three-dimensionalspace at which the user's eyes are verging.

It will be appreciated that gaze direction tracking may be utilized todetermine the virtual content to display to the user; for example,virtual content that is tied to the real world may be adjusted toprovide the correct correspondence with the real world by tracking wherethe user is looking. In addition, in display systems that providevirtual content on different depth planes, the point at which the user'seyes are verging may be utilized to determine the appropriate depthplane on which to display the virtual content.

Some existing techniques for determining eye pose have been limited intracking speed, such that updates to eye pose may be constrained. Thismay cause undesirable latency or jitter in updating content to bedisplayed. Additionally, some existing techniques for determining eyepose have high power requirements. Also, some existing techniquesrequire hardware and/or optical structures which undesirably increasethe complexity of manufacturing processes for forming display systemswith such hardware or systems.

For example, eye-tracking systems utilizing cameras and the analysis ofcaptured images to determine eye pose may undesirably be constrained intracking speed, may utilize large amounts of power, and may require acomplicated and precise arrangement of cameras and light sources. Suchcamera-based systems may use a number of light emitting diodes (LEDs) toproject light at a user's eyes. The LEDs may be positioned on thedisplay system such that light from the LEDs is reflected fromparticular portions of the user's eyes (e.g., a pupil). A camera may bepositioned on the display system to image the eye and determine thepositions of the reflected light. As the user moves his/her eye (e.g.,changes eye pose), the images and positions of reflected light maysimilarly change. Based analysis of the captured images of the eye, thedisplay system may determine an eye pose.

The above-described example technique may allow for the accuratedetermination of a user's eye pose. However, they present certaintechnical challenges. For example, eye tracking speed may be limited bythe rate at which the camera is able to capture and process images(e.g., at a rate of 60 Hz). The constraint on tracking speed may, as anexample, limit an extent to which a presently determined eye pose may berelied upon. As an example, during certain quick movements of an eye(e.g., saccadic movements), the tracking speed may lag behind themovement of the eye, such that displayed content may not match, e.g.,the gaze direction or vergence of the user's eyes. Additionally,limitations on tracking speed may introduce certain visual artifacts.For example, jitter may be introduced when presenting virtual content.Jitter may be caused, at least in part, by the determined eye pose beingperiodically inaccurate as virtual content is displayed.

In addition to the above-described challenges in presenting virtualcontent, existing camera-imaging based techniques for pose determinationmay have electrical and mechanical challenges. With respect toelectrical constraints, the power draw may be high. Indeed, multiplelight sources are required to be driven and a camera (e.g., an infra-redcamera) is required to capture images of a user's eyes. Due to thecomplexity of image information, there is an added processing aspectwhich requires power to analyze each image. This power requirement is inaddition to the power necessary for presenting virtual content. Thus,the portability and battery life of a display using such camera-imagingbased techniques may be undesirably low. With respect to mechanicalconstraints, there may be a complexity associated with positioning theLEDs and camera. For example, the LEDs may need to be aligned such thatthey project light onto certain positions of a user's eye. As anotherexample, the camera may need to be aligned such that it obtains imagesin which all, or a portion, of the LEDs are visible in each image of theuser's eye regardless of eye pose.

As discussed herein, various embodiments provide enhanced techniques andsystems for tracking a user's eyes and advantageously address one ormore of the above-noted technical concerns. For example, the eyetracking techniques may enable tracking at exceptionally high speeds(e.g., 1 kHz, 10 kHz, and so on). In some embodiments, the eye trackingtechniques described herein may use only one light source per eye. Forexample, a diode (e.g., vertical-cavity surface-emitting laser diode),or other light emitting device, may be used for one or more eyes. Incontrast to the requirement of a camera, the techniques described hereinmay use a threshold number of light detectors (e.g., photodiodes,phototransistors, and so on) to detect the amount of reflected incidentlight and process the light intensity signal provided by this reflectedlight, rather than image the eye. Thus, the power requirements may besubstantially less (e.g., an order of magnitude or more less).Additionally, the positioning of the diode and light detectors may besubstantially simpler as compared to the above-described technique,since pose detection is based upon the pattern of detected lightintensity over time, rather than an image analysis of the preciselocations of reflected light in a captured image.

To determine eye pose for a user's eye, the technique described hereinmay scan light, such as a particular light pattern, across the user'seye. As an example, the light pattern may be projected such that itscans (e.g., sweeps) across the user's eye along a horizontal axis(which may be understood to extend through the centers of the user'sleft and right eyes). In some embodiments, the light pattern may includea line of light or multiple light spots that form a line that extendsvertically at less than a 90° angle over the user's eye. For example,the light pattern may extend vertically from a lower portion of theuser's eye to an upper portion of the eye. This light pattern may thenbe moved along the horizontal axis such that it scans the width of theuser's eye or a portion thereof. In some other embodiments, scanning thelight pattern across the user's eyes may involve moving the lightpattern along a vertical axis across the height of the user's eye.

As will be described below, a moveable reflector (e.g., amicroelectromechanical systems (MEMS) mirror) may be used to causescanning of the light pattern. In some embodiments, the moveablereflector may have a diffractive grating. Light from a light source maybe directed to the diffractive grating (also referred to as adiffraction grating), such that a particular light pattern is created.The moveable reflector may then move (e.g., rotate) about one or moreaxes, such that the light pattern is scanned across the user's eye asdescribed above. In some embodiments, the moveable reflector may moveabout a single axis. For instance, in some such embodiments, themoveable reflector may be a one-dimensional MEMs mirror, and the lightpattern employed may vary spatially in at least one other dimension.

In some embodiments, the light pattern may be a “V” pattern. An exampleof such a light pattern is illustrated in FIGS. 10A-10B and described inmore detail herein. This example pattern may include two portions, whicheach extend from a lower portion of the user's eye to an upper portionalong a vertical axis. Each portion, however, may extend across adifferent horizontal portion of the user's eye. For example, eachportion may be an angled line extending in opposite horizontaldirections from the same lower portion (e.g., the two portions of thelight pattern may form a “V”).

As another example, a first portion of the light pattern may be scannedhorizontally across the user's eye and then a second portion of thelight pattern may also be scanned horizontally across the user's eye.The first and second portions may be the two legs of a “V” pattern insome embodiments. For example, the first portion may the right leg ofthe “V”, such that an upper end leads a lower end of the first portion(herein referred to as an “alpha” portion) across the eye. A secondportion of the light pattern (the left leg of the “V”) may similarly bescanned horizontally across the user's eye such that a lower end leadsan upper end of the second portion (herein referred to as a “beta”portion). It will be appreciated that the first and second portionsextend in different directions. In some embodiments, the “V” shape maybe inverted, to assume an “A” shape.

It will be appreciated that other light patterns may be used and fallwithin the scope of the disclosure herein. In some embodiments, thereflector may have a plurality of diffractive gratings that providedifferent light patterns depending upon the diffractive grating thatlight from a light source is incident.

The user's eye may reflect the light pattern directed thereon by themoveable reflector. To determine eye pose, the display system may uselight detectors to measure information (e.g., the intensity of lightincident on the light detector) associated with the reflection. As anexample, the display system may use photodiodes to convert receivedlight into respective electrical currents. These photodiodes maypreferably be on the display system at different positions relative tothe eye. An example orientation of photodiodes is illustrated in FIG.11. Each photodiode, located at different locations, receives differentreflected light from the eye, and converts the different received lightinto a different pattern or plot of electrical current versus time asthe light pattern is scanned across the eye. For ease of reference, theintensity of reflected light detected by a light detector at differentpoints in time, as the light pattern is scanned across the eye, isreferred to herein as a light intensity pattern. In some embodiments,the light intensity pattern may correspond to a pattern defined by orderived from electrical current at different points in time or differentpositions during the scan, where the reflected light is detected by alight sensor (e.g., a photodiode) that converts the light to electricalcurrent. In some embodiments, each of one or more of the light detectorsin the display system may be electrically coupled to generate a voltageindicative of the intensity of light incident on the respective lightdetector. In at least some of these embodiments, one or morephotodiodes, phototransistors, and/or photoresistors may be used aslight detectors in the display system.

Thus, for each scan of a light pattern across a user's eye, there may bea multitude of resulting light intensity patterns, each pattern detectedby a different light detector. As discussed herein, the display systemmay use these light intensity patterns to determine an eye pose for theuser's eye. It will be appreciated that different portions of the user'seye may cause light to be reflected differently (due to asymmetries inthe shape of the eye and/or differences in the composition of differentportions of the eye). Thus, for a given orientation of a user's eye, theresulting collection of light intensity patterns obtained from thedifferent light detectors may be substantially unique; that is, a giveneye pose may have a set of unique “signature” defined by the collectionof light intensity patterns. Using a threshold number of these lightintensity patterns, the display system may determine an eye pose bydetermining the eye post associated with the light intensity patterns.

In some embodiments, the light intensity pattern may include lighthaving different properties in order to efficiently provide a pluralityof different, differentiated signals per pass across the eye. Forexample, the light of the pattern may include a plurality of rows oflight, each having, for example, different wavelengths or differentpolarizations. In some embodiments, each row of light may include aplurality of beams of light, for example, a row of light formed byconverging beams, a row of light formed by collimated beams, and/or arow of light formed by diverging beams.

To determine an eye pose, in some embodiments, the display system mayaccess stored information usable to correlate light intensity patternsto eye pose. For example, a machine learning model may be used todetermine an eye pose based on an input of light intensity patterns.Optionally, the stored information may represent light intensitypatterns which are known to be associated with certain eye poses. Insome embodiments, the display system may determine eye pose based onanalyzing the light intensity patterns. For example, the display systemmay use peaks, valleys, rates of curvature, and so on, as represented inthe light intensity patterns to ascertain an eye pose. In this example,the display system may correlate among the different light intensitypatterns to determine the eye pose.

Thus, various embodiments provide improvements and address technicalchallenges associate with eye tracking or eye pose determinations indisplay systems. As described above, the techniques described herein mayallow for technical efficiencies. For example, a frequency or rate atwhich eye poses is determined may be increased. This increased frequencymay allow for improved visual fidelity, realism, and viewing comfortwhen using a display system. Additionally, power requirements andmechanical alignment complexities may be reduced.

Advantageously, it will be appreciated that the light intensity patternscontain additional information which may be used for other purposes. Forexample, as discussed herein, different portions of the eye (e.g., thesclera, the iris, and the pupil) have different reflectivity, whichprovide different levels of reflected light intensities. These differentreflected liabilities may be utilized to determine the positions and/orsizes of physiological features of the eye (e.g., the iris and/or thepupil). In addition, in some embodiments, the display system maydetermine the velocity of eye movement, e.g., the velocity of saccades,which may be useful for predicting the position of the eye after asaccade. In some embodiments, this prediction may be utilized as a checkon the detected eye pose.

Reference will now be made to the drawings, in which like referencenumerals refer to like parts throughout. Unless indicated otherwise, thedrawings are schematic and not necessarily drawn to scale.

Example Display Systems

FIG. 2 illustrates a conventional display system for simulatingthree-dimensional imagery for a user. It will be appreciated that auser's eyes are spaced apart and that, when looking at a real object inspace, each eye will have a slightly different view of the object andmay form an image of the object at different locations on the retina ofeach eye. This may be referred to as binocular disparity and may beutilized by the human visual system to provide a perception of depth.Conventional display systems simulate binocular disparity by presentingtwo distinct images 190, 200 with slightly different views of the samevirtual object—one for each eye 210, 220—corresponding to the views ofthe virtual object that would be seen by each eye were the virtualobject a real object at a desired depth. These images provide binocularcues that the user's visual system may interpret to derive a perceptionof depth.

With continued reference to FIG. 2, the images 190, 200 are spaced fromthe eyes 210, 220 by a distance 230 on a z-axis. The z-axis is parallelto the optical axis of the viewer with their eyes fixated on an objectat optical infinity directly ahead of the viewer. The images 190, 200are flat and at a fixed distance from the eyes 210, 220. Based on theslightly different views of a virtual object in the images presented tothe eyes 210, 220, respectively, the eyes may naturally rotate such thatan image of the object falls on corresponding points on the retinas ofeach of the eyes, to maintain single binocular vision. This rotation maycause the lines of sight of each of the eyes 210, 220 to converge onto apoint in space at which the virtual object is perceived to be present.As a result, providing three-dimensional imagery conventionally involvesproviding binocular cues that may manipulate the vergence of the user'seyes 210, 220, and that the human visual system interprets to provide aperception of depth.

Generating a realistic and comfortable perception of depth ischallenging, however. It will be appreciated that light from objects atdifferent distances from the eyes have wavefronts with different amountsof divergence. FIGS. 3A-3C illustrate relationships between distance andthe divergence of light rays. The distance between the object and theeye 210 is represented by, in order of decreasing distance, R1, R2, andR3. As shown in FIGS. 3A-3C, the light rays become more divergent asdistance to the object decreases. Conversely, as distance increases, thelight rays become more collimated. Stated another way, it will be saidthat the light field produced by a point (the object or a part of theobject) has a spherical wavefront curvature, which is a function of howfar away the point is from the eye of the user. The curvature increaseswith decreasing distance between the object and the eye 210. While onlya single eye 210 is illustrated for clarity of illustration in FIGS.3A-3C and other figures herein, the discussions regarding eye 210 may beapplied to both eyes 210 and 220 of a viewer.

With continued reference to FIGS. 3A-3C, light from an object that theviewer's eyes are fixated on may have different degrees of wavefrontdivergence. Due to the different amounts of wavefront divergence, thelight may be focused differently by the lens of the eye, which in turnmay require the lens to assume different shapes to form a focused imageon the retina of the eye. Where a focused image is not formed on theretina, the resulting retinal blur acts as a cue to accommodation thatcauses a change in the shape of the lens of the eye until a focusedimage is formed on the retina. For example, the cue to accommodation maytrigger the ciliary muscles surrounding the lens of the eye to relax orcontract, thereby modulating the force applied to the suspensoryligaments holding the lens, thus causing the shape of the lens of theeye to change until retinal blur of an object of fixation is eliminatedor minimized, thereby forming a focused image of the object of fixationon the retina (e.g., fovea) of the eye. The process by which the lens ofthe eye changes shape may be referred to as accommodation, and the shapeof the lens of the eye required to form a focused image of the object offixation on the retina (e.g., fovea) of the eye may be referred to as anaccommodative state.

With reference now to FIG. 4A, a representation of theaccommodation-vergence response of the human visual system isillustrated. The movement of the eyes to fixate on an object causes theeyes to receive light from the object, with the light forming an imageon each of the retinas of the eyes. The presence of retinal blur in theimage formed on the retina may provide a cue to accommodation, and therelative locations of the image on the retinas may provide a cue tovergence. The cue to accommodation causes accommodation to occur,resulting in the lenses of the eyes each assuming a particularaccommodative state that forms a focused image of the object on theretina (e.g., fovea) of the eye. On the other hand, the cue to vergencecauses vergence movements (rotation of the eyes) to occur such that theimages formed on each retina of each eye are at corresponding retinalpoints that maintain single binocular vision. In these positions, theeyes may be said to have assumed a particular vergence state. Withcontinued reference to FIG. 4A, accommodation may be understood to bethe process by which the eye achieves a particular accommodative state,and vergence may be understood to be the process by which the eyeachieves a particular vergence state. As indicated in FIG. 4A, theaccommodative and vergence states of the eyes may change if the userfixates on another object. For example, the accommodated state maychange if the user fixates on a new object at a different depth on thez-axis.

Without being limited by theory, it is believed that viewers of anobject may perceive the object as being “three-dimensional” due to acombination of vergence and accommodation. As noted above, vergencemovements (e.g., rotation of the eyes so that the pupils move toward oraway from each other to converge the lines of sight of the eyes tofixate upon an object) of the two eyes relative to each other areclosely associated with accommodation of the lenses of the eyes. Undernormal conditions, changing the shapes of the lenses of the eyes tochange focus from one object to another object at a different distancewill automatically cause a matching change in vergence to the samedistance, under a relationship known as the “accommodation-vergencereflex.” Likewise, a change in vergence will trigger a matching changein lens shape under normal conditions.

With reference now to FIG. 4B, examples of different accommodative andvergence states of the eyes are illustrated. The pair of eyes 222 a isfixated on an object at optical infinity, while the pair eyes 222 b arefixated on an object 221 at less than optical infinity. Notably, thevergence states of each pair of eyes is different, with the pair of eyes222 a directed straight ahead, while the pair of eyes 222 converge onthe object 221. The accommodative states of the eyes forming each pairof eyes 222 a and 222 b are also different, as represented by thedifferent shapes of the lenses 210 a, 220 a.

Undesirably, many users of conventional “3-D” display systems find suchconventional systems to be uncomfortable or may not perceive a sense ofdepth at all due to a mismatch between accommodative and vergence statesin these displays. As noted above, many stereoscopic or “3-D” displaysystems display a scene by providing slightly different images to eacheye. Such systems are uncomfortable for many viewers, since they, amongother things, simply provide different presentations of a scene andcause changes in the vergence states of the eyes, but without acorresponding change in the accommodative states of those eyes. Rather,the images are shown by a display at a fixed distance from the eyes,such that the eyes view all the image information at a singleaccommodative state. Such an arrangement works against the“accommodation-vergence reflex” by causing changes in the vergence statewithout a matching change in the accommodative state. This mismatch isbelieved to cause viewer discomfort. Display systems that provide abetter match between accommodation and vergence may form more realisticand comfortable simulations of three-dimensional imagery.

Without being limited by theory, it is believed that the human eyetypically may interpret a finite number of depth planes to provide depthperception. Consequently, a highly believable simulation of perceiveddepth may be achieved by providing, to the eye, different presentationsof an image corresponding to each of these limited numbers of depthplanes. In some embodiments, the different presentations may provideboth cues to vergence and matching cues to accommodation, therebyproviding physiologically correct accommodation-vergence matching.

With continued reference to FIG. 4B, two depth planes 240, correspondingto different distances in space from the eyes 210, 220, are illustrated.For a given depth plane 240, vergence cues may be provided by thedisplaying of images of appropriately different perspectives for eacheye 210, 220. In addition, for a given depth plane 240, light formingthe images provided to each eye 210, 220 may have a wavefront divergencecorresponding to a light field produced by a point at the distance ofthat depth plane 240.

In the illustrated embodiment, the distance, along the z-axis, of thedepth plane 240 containing the point 221 is 1 m. As used herein,distances or depths along the z-axis may be measured with a zero-pointlocated at the exit pupils of the user's eyes. Thus, a depth plane 240located at a depth of 1 m corresponds to a distance of 1 m away from theexit pupils of the user's eyes, on the optical axis of those eyes withthe eyes directed towards optical infinity. As an approximation, thedepth or distance along the z-axis may be measured from the display infront of the user's eyes (e.g., from the surface of a waveguide), plus avalue for the distance between the device and the exit pupils of theuser's eyes. That value may be called the eye relief and corresponds tothe distance between the exit pupil of the user's eye and the displayworn by the user in front of the eye. In practice, the value for the eyerelief may be a normalized value used generally for all viewers. Forexample, the eye relief may be assumed to be 20 mm and a depth planethat is at a depth of 1 m may be at a distance of 980 mm in front of thedisplay.

With reference now to FIGS. 4C and 4D, examples of matchedaccommodation-vergence distances and mismatched accommodation-vergencedistances are illustrated, respectively. As illustrated in FIG. 4C, thedisplay system may provide images of a virtual object to each eye 210,220. The images may cause the eyes 210, 220 to assume a vergence statein which the eyes converge on a point 15 on a depth plane 240. Inaddition, the images may be formed by a light having a wavefrontcurvature corresponding to real objects at that depth plane 240. As aresult, the eyes 210, 220 assume an accommodative state in which theimages are in focus on the retinas of those eyes. Thus, the user mayperceive the virtual object as being at the point 15 on the depth plane240.

It will be appreciated that each of the accommodative and vergencestates of the eyes 210, 220 are associated with a particular distance onthe z-axis. For example, an object at a particular distance from theeyes 210, 220 causes those eyes to assume particular accommodativestates based upon the distances of the object. The distance associatedwith a particular accommodative state may be referred to as theaccommodation distance, A_(d). Similarly, there are particular vergencedistances, V_(d), associated with the eyes in particular vergencestates, or positions relative to one another. Where the accommodationdistance and the vergence distance match, the relationship betweenaccommodation and vergence may be said to be physiologically correct.This is considered to be the most comfortable scenario for a viewer.

In stereoscopic displays, however, the accommodation distance and thevergence distance may not always match. For example, as illustrated inFIG. 4D, images displayed to the eyes 210, 220 may be displayed withwavefront divergence corresponding to depth plane 240, and the eyes 210,220 may assume a particular accommodative state in which the points 15a, 15 b on that depth plane are in focus. However, the images displayedto the eyes 210, 220 may provide cues for vergence that cause the eyes210, 220 to converge on a point 15 that is not located on the depthplane 240. As a result, the accommodation distance corresponds to thedistance from the exit pupils of the eyes 210, 220 to the depth plane240, while the vergence distance corresponds to the larger distance fromthe exit pupils of the eyes 210, 220 to the point 15, in someembodiments. The accommodation distance is different from the vergencedistance. Consequently, there is an accommodation-vergence mismatch.Such a mismatch is considered undesirable and may cause discomfort inthe user. It will be appreciated that the mismatch corresponds todistance (e.g., V_(d)−A_(d)) and may be characterized using diopters.

In some embodiments, it will be appreciated that a reference point otherthan exit pupils of the eyes 210, 220 may be utilized for determiningdistance for determining accommodation-vergence mismatch, so long as thesame reference point is utilized for the accommodation distance and thevergence distance. For example, the distances could be measured from thecornea to the depth plane, from the retina to the depth plane, from theeyepiece (e.g., a waveguide of the display device) to the depth plane,and so on.

Without being limited by theory, it is believed that users may stillperceive accommodation-vergence mismatches of up to about 0.25 diopter,up to about 0.33 diopter, and up to about 0.5 diopter as beingphysiologically correct, without the mismatch itself causing significantdiscomfort. In some embodiments, display systems disclosed herein (e.g.,the display system 250, FIG. 6) present images to the viewer havingaccommodation-vergence mismatch of about 0.5 diopter or less. In someother embodiments, the accommodation-vergence mismatch of the imagesprovided by the display system is about 0.33 diopter or less. In yetother embodiments, the accommodation-vergence mismatch of the imagesprovided by the display system is about 0.25 diopter or less, includingabout 0.1 diopter or less.

FIG. 5 illustrates aspects of an approach for simulatingthree-dimensional imagery by modifying wavefront divergence. The displaysystem includes a waveguide 270 that is configured to receive light 770that is encoded with image information, and to output that light to theuser's eye 210. The waveguide 270 may output the light 650 with adefined amount of wavefront divergence corresponding to the wavefrontdivergence of a light field produced by a point on a desired depth plane240. In some embodiments, the same amount of wavefront divergence isprovided for all objects presented on that depth plane. In addition, itwill be illustrated that the other eye of the user may be provided withimage information from a similar waveguide.

In some embodiments, a single waveguide may be configured to outputlight with a set amount of wavefront divergence corresponding to asingle or limited number of depth planes and/or the waveguide may beconfigured to output light of a limited range of wavelengths.Consequently, in some embodiments, a plurality or stack of waveguidesmay be utilized to provide different amounts of wavefront divergence fordifferent depth planes and/or to output light of different ranges ofwavelengths. As used herein, it will be appreciated at a depth plane maybe planar or may follow the contours of a curved surface.

FIG. 6 illustrates an example of a waveguide stack for outputting imageinformation to a user. A display system 250 includes a stack ofwaveguides, or stacked waveguide assembly, 260 that may be utilized toprovide three-dimensional perception to the eye/brain using a pluralityof waveguides 270, 280, 290, 300, 310. It will be appreciated that thedisplay system 250 may be considered a light field display in someembodiments. In addition, the waveguide assembly 260 may also bereferred to as an eyepiece.

In some embodiments, the display system 250 may be configured to providesubstantially continuous cues to vergence and multiple discrete cues toaccommodation. The cues to vergence may be provided by displayingdifferent images to each of the eyes of the user, and the cues toaccommodation may be provided by outputting the light that forms theimages with selectable discrete amounts of wavefront divergence. Statedanother way, the display system 250 may be configured to output lightwith variable levels of wavefront divergence. In some embodiments, eachdiscrete level of wavefront divergence corresponds to a particular depthplane and may be provided by a particular one of the waveguides 270,280, 290, 300, 310.

With continued reference to FIG. 6, the waveguide assembly 260 may alsoinclude a plurality of features 320, 330, 340, 350 between thewaveguides. In some embodiments, the features 320, 330, 340, 350 may beone or more lenses. The waveguides 270, 280, 290, 300, 310 and/or theplurality of lenses 320, 330, 340, 350 may be configured to send imageinformation to the eye with various levels of wavefront curvature orlight ray divergence. Each waveguide level may be associated with aparticular depth plane and may be configured to output image informationcorresponding to that depth plane. Image injection devices 360, 370,380, 390, 400 may function as a source of light for the waveguides andmay be utilized to inject image information into the waveguides 270,280, 290, 300, 310, each of which may be configured, as describedherein, to distribute incoming light across each respective waveguide,for output toward the eye 210. Light exits an output surface 410, 420,430, 440, 450 of the image injection devices 360, 370, 380, 390, 400 andis injected into a corresponding input surface 460, 470, 480, 490, 500of the waveguides 270, 280, 290, 300, 310. In some embodiments, each ofthe input surfaces 460, 470, 480, 490, 500 may be an edge of acorresponding waveguide, or may be part of a major surface of thecorresponding waveguide (that is, one of the waveguide surfaces directlyfacing the world 510 or the viewer's eye 210). In some embodiments, asingle beam of light (e.g., a collimated beam) may be injected into eachwaveguide to output an entire field of cloned collimated beams that aredirected toward the eye 210 at particular angles (and amounts ofdivergence) corresponding to the depth plane associated with aparticular waveguide. In some embodiments, a single one of the imageinjection devices 360, 370, 380, 390, 400 may be associated with andinject light into a plurality (e.g., three) of the waveguides 270, 280,290, 300, 310.

In some embodiments, the image injection devices 360, 370, 380, 390, 400are discrete displays that each produce image information for injectioninto a corresponding waveguide 270, 280, 290, 300, 310, respectively. Insome other embodiments, the image injection devices 360, 370, 380, 390,400 are the output ends of a single multiplexed display which may, e.g.,pipe image information via one or more optical conduits (such as fiberoptic cables) to each of the image injection devices 360, 370, 380, 390,400. It will be appreciated that the image information provided by theimage injection devices 360, 370, 380, 390, 400 may include light ofdifferent wavelengths, or colors (e.g., different component colors, asdiscussed herein).

In some embodiments, the light injected into the waveguides 270, 280,290, 300, 310 is encoded with image information and provided by a lightprojector system 1010, as discussed further herein. In some embodiments,the light projector system 1010 may comprise one or more emissive pixelarrays. It will be appreciated that the emissive pixel arrays may eachcomprise a plurality of light-emitting pixels, which may be configuredto emit light of varying intensities and colors. It will be appreciatedthat the image injection devices 360, 370, 380, 390, 400 are illustratedschematically and, in some embodiments, these image injection devicesmay represent different light paths and locations in a common projectionsystem configured to output light into associated ones of the waveguides270, 280, 290, 300, 310. In some embodiments, the waveguides of thewaveguide assembly 260 may function as ideal lens while relaying lightinjected into the waveguides out to the user's eyes. In this conception,the object may be the pixel array of the light projector system 1010 andthe image may be the image on the depth plane.

A controller 560 controls the operation of one or more of the stackedwaveguide assembly 260, including operation of the image injectiondevices 360, 370, 380, 390, 400, the light projection system 1010. Insome embodiments, the controller 560 is part of the local dataprocessing module 140. The controller 560 includes programming (e.g.,instructions in a non-transitory medium) that regulates the timing andprovision of image information to the waveguides 270, 280, 290, 300, 310according to, e.g., any of the various schemes disclosed herein. In someembodiments, the controller may be a single integral device, or adistributed system connected by wired or wireless communicationchannels. The controller 560 may be part of the processing modules 140or 150 (FIG. 9D) in some embodiments.

With continued reference to FIG. 6, the waveguides 270, 280, 290, 300,310 may be configured to propagate light within each respectivewaveguide by total internal reflection (TIR). The waveguides 270, 280,290, 300, 310 may each be planar or have another shape (e.g., curved),with major top and bottom surfaces and edges extending between thosemajor top and bottom surfaces. In the illustrated configuration, thewaveguides 270, 280, 290, 300, 310 may each include out-coupling opticalelements 570, 580, 590, 600, 610 that are configured to extract lightout of a waveguide by redirecting the light, propagating within eachrespective waveguide, out of the waveguide to output image informationto the eye 210. Extracted light may also be referred to as out-coupledlight and the out-coupling optical elements light may also be referredto light extracting optical elements. An extracted beam of light may beoutputted by the waveguide at locations at which the light propagatingin the waveguide strikes a light extracting optical element. Theout-coupling optical elements 570, 580, 590, 600, 610 may, for example,be gratings, including diffractive optical features, as discussedfurther herein. While illustrated disposed at the bottom major surfacesof the waveguides 270, 280, 290, 300, 310, for ease of description anddrawing clarity, in some embodiments, the out-coupling optical elements570, 580, 590, 600, 610 may be disposed at the top and/or bottom majorsurfaces, and/or may be disposed directly in the volume of thewaveguides 270, 280, 290, 300, 310, as discussed further herein. In someembodiments, the out-coupling optical elements 570, 580, 590, 600, 610may be formed in a layer of material that is attached to a transparentsubstrate to form the waveguides 270, 280, 290, 300, 310. In some otherembodiments, the waveguides 270, 280, 290, 300, 310 may be a monolithicpiece of material and the out-coupling optical elements 570, 580, 590,600, 610 may be formed on a surface and/or in the interior of that pieceof material.

With continued reference to FIG. 6, as discussed herein, each waveguide270, 280, 290, 300, 310 is configured to output light to form an imagecorresponding to a particular depth plane. For example, the waveguide270 nearest the eye may be configured to deliver collimated light (whichwas injected into such waveguide 270), to the eye 210. The collimatedlight may be representative of the optical infinity focal plane. Thenext waveguide up 280 may be configured to send out collimated lightwhich passes through the first lens 350 (e.g., a negative lens) beforeit may reach the eye 210; such first lens 350 may be configured tocreate a slight convex wavefront curvature so that the eye/braininterprets light coming from that next waveguide up 280 as coming from afirst focal plane closer inward toward the eye 210 from opticalinfinity. Similarly, the third up waveguide 290 passes its output lightthrough both the first 350 and second 340 lenses before reaching the eye210; the combined optical power of the first 350 and second 340 lensesmay be configured to create another incremental amount of wavefrontcurvature so that the eye/brain interprets light coming from the thirdwaveguide 290 as coming from a second focal plane that is even closerinward toward the person from optical infinity than was light from thenext waveguide up 280.

The other waveguide layers 300, 310 and lenses 330, 320 are similarlyconfigured, with the highest waveguide 310 in the stack sending itsoutput through all of the lenses between it and the eye for an aggregatefocal power representative of the closest focal plane to the person. Tocompensate for the stack of lenses 320, 330, 340, 350 whenviewing/interpreting light coming from the world 510 on the other sideof the stacked waveguide assembly 260, a compensating lens layer 620 maybe disposed at the top of the stack to compensate for the aggregatepower of the lens stack 320, 330, 340, 350 below. Such a configurationprovides as many perceived focal planes as there are availablewaveguide/lens pairings. Both the out-coupling optical elements of thewaveguides and the focusing aspects of the lenses may be static (i.e.,not dynamic or electro-active). In some alternative embodiments, eitheror both may be dynamic using electro-active features.

In some embodiments, two or more of the waveguides 270, 280, 290, 300,310 may have the same associated depth plane. For example, multiplewaveguides 270, 280, 290, 300, 310 may be configured to output imagesset to the same depth plane, or multiple subsets of the waveguides 270,280, 290, 300, 310 may be configured to output images set to the sameplurality of depth planes, with one set for each depth plane. This mayprovide advantages for forming a tiled image to provide an expandedfield of view at those depth planes.

With continued reference to FIG. 6, the out-coupling optical elements570, 580, 590, 600, 610 may be configured to both redirect light out oftheir respective waveguides and to output this light with theappropriate amount of divergence or collimation for a particular depthplane associated with the waveguide. As a result, waveguides havingdifferent associated depth planes may have different configurations ofout-coupling optical elements 570, 580, 590, 600, 610, which outputlight with a different amount of divergence depending on the associateddepth plane. In some embodiments, the light extracting optical elements570, 580, 590, 600, 610 may be volumetric or surface features, which maybe configured to output light at specific angles. For example, the lightextracting optical elements 570, 580, 590, 600, 610 may be volumeholograms, surface holograms, and/or diffraction gratings. In someembodiments, the features 320, 330, 340, 350 may not be lenses; rather,they may simply be spacers (e.g., cladding layers and/or structures forforming air gaps).

In some embodiments, the out-coupling optical elements 570, 580, 590,600, 610 are diffractive features that form a diffraction pattern, or“diffractive optical element” (also referred to herein as a “DOE”).Preferably, the DOE's have a sufficiently low diffraction efficiency sothat only a portion of the light of the beam is deflected away towardthe eye 210 with each intersection of the DOE, while the rest continuesto move through a waveguide via TIR. The light carrying the imageinformation is thus divided into a number of related exit beams thatexit the waveguide at a multiplicity of locations and the result is afairly uniform pattern of exit emission toward the eye 210 for thisparticular collimated beam bouncing around within a waveguide.

In some embodiments, one or more DOEs may be switchable between “on”states in which they actively diffract, and “off” states in which theydo not significantly diffract. For instance, a switchable DOE maycomprise a layer of polymer dispersed liquid crystal, in whichmicrodroplets comprise a diffraction pattern in a host medium, and therefractive index of the microdroplets may be switched to substantiallymatch the refractive index of the host material (in which case thepattern does not appreciably diffract incident light) or themicrodroplet may be switched to an index that does not match that of thehost medium (in which case the pattern actively diffracts incidentlight).

In some embodiments, a camera assembly 630 (e.g., a digital camera,including visible light and infrared light cameras) may be provided tocapture images of the eye 210 and/or tissue around the eye 210 to, e.g.,detect user inputs and/or to monitor the physiological state of theuser. As used herein, a camera may be any image capture device. In someembodiments, the camera assembly 630 may include an image capture deviceand a light source to project light (e.g., infrared light) to the eye,which may then be reflected by the eye and detected by the image capturedevice. In some embodiments, the camera assembly 630 may be attached tothe frame 80 (FIG. 9D) and may be in electrical communication with theprocessing modules 140 and/or 150, which may process image informationfrom the camera assembly 630. In some embodiments, one camera assembly630 may be utilized for each eye, to separately monitor each eye.

With reference now to FIG. 7, an example of exit beams outputted by awaveguide is shown. One waveguide is illustrated, but it will beappreciated that other waveguides in the waveguide assembly 260 (FIG. 6)may function similarly, where the waveguide assembly 260 includesmultiple waveguides. Light 640 is injected into the waveguide 270 at theinput surface 460 of the waveguide 270 and propagates within thewaveguide 270 by TIR. At points where the light 640 impinges on the DOE570, a portion of the light exits the waveguide as exit beams 650. Theexit beams 650 are illustrated as substantially parallel but, asdiscussed herein, they may also be redirected to propagate to the eye210 at an angle (e.g., forming divergent exit beams), depending on thedepth plane associated with the waveguide 270. It will be appreciatedthat substantially parallel exit beams may be indicative of a waveguidewith out-coupling optical elements that out-couple light to form imagesthat appear to be set on a depth plane at a large distance (e.g.,optical infinity) from the eye 210. Other waveguides or other sets ofout-coupling optical elements may output an exit beam pattern that ismore divergent, which would require the eye 210 to accommodate to acloser distance to bring it into focus on the retina and would beinterpreted by the brain as light from a distance closer to the eye 210than optical infinity.

In some embodiments, a full color image may be formed at each depthplane by overlaying images in each of the component colors, e.g., threeor more component colors. FIG. 8 illustrates an example of a stackedwaveguide assembly in which each depth plane includes images formedusing multiple different component colors. The illustrated embodimentshows depth planes 240 a-240 f, although more or fewer depths are alsocontemplated. Each depth plane may have three or more component colorimages associated with it, including: a first image of a first color, G;a second image of a second color, R; and a third image of a third color,B. Different depth planes are indicated in the figure by differentnumbers for diopters (dpt) following the letters G, R, and B. Just asexamples, the numbers following each of these letters indicate diopters(1/m), or inverse distance of the depth plane from a viewer, and eachbox in the figures represents an individual component color image. Insome embodiments, to account for differences in the eye's focusing oflight of different wavelengths, the exact placement of the depth planesfor different component colors may vary. For example, differentcomponent color images for a given depth plane may be placed on depthplanes corresponding to different distances from the user. Such anarrangement may increase visual acuity and user comfort and/or maydecrease chromatic aberrations.

In some embodiments, light of each component color may be outputted by asingle dedicated waveguide and, consequently, each depth plane may havemultiple waveguides associated with it. In such embodiments, each box inthe figures including the letters G, R, or B may be understood torepresent an individual waveguide, and three waveguides may be providedper depth plane where three component color images are provided perdepth plane. While the waveguides associated with each depth plane areshown adjacent to one another in this drawing for ease of description,it will be appreciated that, in a physical device, the waveguides mayall be arranged in a stack with one waveguide per level. In some otherembodiments, multiple component colors may be outputted by the samewaveguide, such that, e.g., only a single waveguide may be provided perdepth plane.

With continued reference to FIG. 8, in some embodiments, G is the colorgreen, R is the color red, and B is the color blue. In some otherembodiments, other colors associated with other wavelengths of light,including magenta and cyan, may be used in addition to or may replaceone or more of red, green, or blue.

It will be appreciated that references to a given color of lightthroughout this disclosure will be understood to encompass light of oneor more wavelengths within a range of wavelengths of light that areperceived by a viewer as being of that given color. For example, redlight may include light of one or more wavelengths in the range of about620-780 nm, green light may include light of one or more wavelengths inthe range of about 492-577 nm, and blue light may include light of oneor more wavelengths in the range of about 435-493 nm.

In some embodiments, the light projection system 1010 (FIG. 6) may beconfigured to emit light of one or more wavelengths outside the visualperception range of the viewer, for example, infrared and/or ultravioletwavelengths. In addition, the in-coupling, out-coupling, and other lightredirecting structures of the waveguides of the display 250 may beconfigured to direct and emit this light out of the display towards theuser's eye 210, e.g., for imaging and/or user stimulation applications.

With reference now to FIG. 9A, in some embodiments, light impinging on awaveguide may need to be redirected to in-couple that light into thewaveguide. An in-coupling optical element may be used to redirect andin-couple the light into its corresponding waveguide. FIG. 9Aillustrates a cross-sectional side view of an example of a plurality orset 660 of stacked waveguides that each includes an in-coupling opticalelement. The waveguides may each be configured to output light of one ormore different wavelengths, or one or more different ranges ofwavelengths. It will be appreciated that the stack 660 may correspond tothe stack 260 (FIG. 6) and the illustrated waveguides of the stack 660may correspond to part of the plurality of waveguides 270, 280, 290,300, 310, except that light from one or more of the image injectiondevices 360, 370, 380, 390, 400 is injected into the waveguides from aposition that requires light to be redirected for in-coupling.

The illustrated set 660 of stacked waveguides includes waveguides 670,680, and 690. Each waveguide includes an associated in-coupling opticalelement (which may also be referred to as a light input area on thewaveguide), with, e.g., in-coupling optical element 700 disposed on amajor surface (e.g., an upper major surface) of waveguide 670,in-coupling optical element 710 disposed on a major surface (e.g., anupper major surface) of waveguide 680, and in-coupling optical element720 disposed on a major surface (e.g., an upper major surface) ofwaveguide 690. In some embodiments, one or more of the in-couplingoptical elements 700, 710, 720 may be disposed on the bottom majorsurface of the respective waveguide 670, 680, 690 (particularly wherethe one or more in-coupling optical elements are reflective, deflectingoptical elements). As illustrated, the in-coupling optical elements 700,710, 720 may be disposed on the upper major surface of their respectivewaveguide 670, 680, 690 (or the top of the next lower waveguide),particularly where those in-coupling optical elements are transmissive,deflecting optical elements. In some embodiments, the in-couplingoptical elements 700, 710, 720 may be disposed in the body of therespective waveguide 670, 680, 690. In some embodiments, as discussedherein, the in-coupling optical elements 700, 710, 720 are wavelengthselective, such that they selectively redirect one or more wavelengthsof light, while transmitting other wavelengths of light. Whileillustrated on one side or corner of their respective waveguide 670,680, 690, it will be appreciated that the in-coupling optical elements700, 710, 720 may be disposed in other areas of their respectivewaveguide 670, 680, 690 in some embodiments.

As illustrated, the in-coupling optical elements 700, 710, 720 may belaterally offset from one another. In some embodiments, each in-couplingoptical element may be offset such that it receives light without thatlight passing through another in-coupling optical element. For example,each in-coupling optical element 700, 710, 720 may be configured toreceive light from a different image injection device 360, 370, 380,390, and 400 as shown in FIG. 6, and may be separated (e.g., laterallyspaced apart) from other in-coupling optical elements 700, 710, 720 suchthat it substantially does not receive light from the other ones of thein-coupling optical elements 700, 710, 720.

Each waveguide also includes associated light distributing elements,with, e.g., light distributing elements 730 disposed on a major surface(e.g., a top major surface) of waveguide 670, light distributingelements 740 disposed on a major surface (e.g., a top major surface) ofwaveguide 680, and light distributing elements 750 disposed on a majorsurface (e.g., a top major surface) of waveguide 690. In some otherembodiments, the light distributing elements 730, 740, 750, may bedisposed on a bottom major surface of associated waveguides 670, 680,690, respectively. In some other embodiments, the light distributingelements 730, 740, 750, may be disposed on both top and bottom majorsurface of associated waveguides 670, 680, 690, respectively; or thelight distributing elements 730, 740, 750, may be disposed on differentones of the top and bottom major surfaces in different associatedwaveguides 670, 680, 690, respectively.

The waveguides 670, 680, 690 may be spaced apart and separated by, e.g.,gas, liquid, and/or solid layers of material. For example, asillustrated, layer 760 a may separate waveguides 670 and 680; and layer760 b may separate waveguides 680 and 690. In some embodiments, thelayers 760 a and 760 b are formed of low refractive index materials(that is, materials having a lower refractive index than the materialforming the immediately adjacent one of waveguides 670, 680, 690).Preferably, the refractive index of the material forming the layers 760a, 760 b is 0.05 or more, or 0.10 or less than the refractive index ofthe material forming the waveguides 670, 680, 690. Advantageously, thelower refractive index layers 760 a, 760 b may function as claddinglayers that facilitate total internal reflection (TIR) of light throughthe waveguides 670, 680, 690 (e.g., TIR between the top and bottom majorsurfaces of each waveguide). In some embodiments, the layers 760 a, 760b are formed of air. While not illustrated, it will be appreciated thatthe top and bottom of the illustrated set 660 of waveguides may includeimmediately neighboring cladding layers.

Preferably, for ease of manufacturing and other considerations, thematerial forming the waveguides 670, 680, 690 are similar or the same,and the material forming the layers 760 a, 760 b are similar or thesame. In some embodiments, the material forming the waveguides 670, 680,690 may be different between one or more waveguides, and/or the materialforming the layers 760 a, 760 b may be different, while still holding tothe various refractive index relationships noted above.

With continued reference to FIG. 9A, light rays 770, 780, 790 areincident on the set 660 of waveguides. It will be appreciated that thelight rays 770, 780, 790 may be injected into the waveguides 670, 680,690 by one or more image injection devices 360, 370, 380, 390, 400 (FIG.6).

In some embodiments, the light rays 770, 780, 790 are intended fordifferent waveguides (e.g., waveguides configured to output light withdifferent amounts of wavefront divergence, and/or configured to outputlight having different properties, such as different wavelengths orcolors). Thus, in some embodiments, the light rays 770, 780, 790 mayhave different properties, e.g., different wavelengths or differentranges of wavelengths, which may correspond to different colors. Thein-coupling optical elements 700, 710, 720 each deflect the incidentlight such that the light propagates through a respective one of thewaveguides 670, 680, 690 by TIR. In some embodiments, the in-couplingoptical elements 700, 710, 720 each selectively deflect one or moreparticular wavelengths of light, while transmitting other wavelengths toan underlying waveguide and associated in-coupling optical element.

For example, in-coupling optical element 700 may be configured todeflect ray 770, which has a first wavelength or range of wavelengths,while transmitting rays 780 and 790, which have different second andthird wavelengths or ranges of wavelengths, respectively. Thetransmitted ray 780 impinges on and is deflected by the in-couplingoptical element 710, which is configured to deflect light of a secondwavelength or range of wavelengths. The ray 790 is deflected by thein-coupling optical element 720, which is configured to selectivelydeflect light of third wavelength or range of wavelengths.

With continued reference to FIG. 9A, the deflected light rays 770, 780,790 are deflected so that they propagate through a correspondingwaveguide 670, 680, 690; that is, the in-coupling optical elements 700,710, 720 of each waveguide deflects light into that correspondingwaveguide 670, 680, 690 to in-couple light into that correspondingwaveguide. The light rays 770, 780, 790 are deflected at angles thatcause the light to propagate through the respective waveguide 670, 680,690 by TIR. The light rays 770, 780, 790 propagate through therespective waveguide 670, 680, 690 by TIR until impinging on thewaveguide's corresponding light distributing elements 730, 740, 750.

With reference now to FIG. 9B, a perspective view of an example of theplurality of stacked waveguides of FIG. 9A is illustrated. As notedabove, the in-coupled light rays 770, 780, 790, are deflected by thein-coupling optical elements 700, 710, 720, respectively, and thenpropagate by TIR within the waveguides 670, 680, 690, respectively. Thelight rays 770, 780, 790 then impinge on the light distributing elements730, 740, 750, respectively. The light distributing elements 730, 740,750 deflect the light rays 770, 780, 790 so that they propagate towardsthe out-coupling optical elements 800, 810, 820, respectively.

In some embodiments, the light distributing elements 730, 740, 750 areorthogonal pupil expanders (OPE's). In some embodiments, the OPE'sdeflect or distribute light to the out-coupling optical elements 800,810, 820 and, in some embodiments, may also increase the beam or spotsize of this light as it propagates to the out-coupling opticalelements. In some embodiments, the light distributing elements 730, 740,750 may be omitted and the in-coupling optical elements 700, 710, 720may be configured to deflect light directly to the out-coupling opticalelements 800, 810, 820. For example, with reference to FIG. 9A, thelight distributing elements 730, 740, 750 may be replaced without-coupling optical elements 800, 810, 820, respectively. In someembodiments, the out-coupling optical elements 800, 810, 820 are exitpupils (EP's) or exit pupil expanders (EPE's) that direct light in aviewer's eye 210 (FIG. 7). It will be appreciated that the OPE's may beconfigured to increase the dimensions of the eye box in at least oneaxis and the EPE's may be to increase the eye box in an axis crossing,e.g., orthogonal to, the axis of the OPEs. For example, each OPE may beconfigured to redirect a portion of the light striking the OPE to an EPEof the same waveguide, while allowing the remaining portion of the lightto continue to propagate down the waveguide. Upon impinging on the OPEagain, another portion of the remaining light is redirected to the EPE,and the remaining portion of that portion continues to propagate furtherdown the waveguide, and so on. Similarly, upon striking the EPE, aportion of the impinging light is directed out of the waveguide towardsthe user, and a remaining portion of that light continues to propagatethrough the waveguide until it strikes the EP again, at which timeanother portion of the impinging light is directed out of the waveguide,and so on. Consequently, a single beam of in-coupled light may be“replicated” each time a portion of that light is redirected by an OPEor EPE, thereby forming a field of cloned beams of light, as shown inFIG. 6. In some embodiments, the OPE and/or EPE may be configured tomodify a size of the beams of light.

Accordingly, with reference to FIGS. 9A and 9B, in some embodiments, theset 660 of waveguides includes waveguides 670, 680, 690; in-couplingoptical elements 700, 710, 720; light distributing elements (e.g.,OPE's) 730, 740, 750; and out-coupling optical elements (e.g., EP's)800, 810, 820 for each component color. The waveguides 670, 680, 690 maybe stacked with an air gap/cladding layer between each one. Thein-coupling optical elements 700, 710, 720 redirect or deflect incidentlight (with different in-coupling optical elements receiving light ofdifferent wavelengths) into its waveguide. The light then propagates atan angle which will result in TIR within the respective waveguide 670,680, 690. In the example shown, light ray 770 (e.g., blue light) isdeflected by the first in-coupling optical element 700, and thencontinues to bounce down the waveguide, interacting with the lightdistributing element (e.g., OPE's) 730 and then the out-coupling opticalelement (e.g., EPs) 800, in a manner described earlier. The light rays780 and 790 (e.g., green and red light, respectively) will pass throughthe waveguide 670, with light ray 780 impinging on and being deflectedby in-coupling optical element 710. The light ray 780 then bounces downthe waveguide 680 via TIR, proceeding on to its light distributingelement (e.g., OPEs) 740 and then the out-coupling optical element(e.g., EP's) 810. Finally, light ray 790 (e.g., red light) passesthrough the waveguide 690 to impinge on the light in-coupling opticalelements 720 of the waveguide 690. The light in-coupling opticalelements 720 deflect the light ray 790 such that the light raypropagates to light distributing element (e.g., OPEs) 750 by TIR, andthen to the out-coupling optical element (e.g., EPs) 820 by TIR. Theout-coupling optical element 820 then finally out-couples the light ray790 to the viewer, who also receives the out-coupled light from theother waveguides 670, 680.

FIG. 9C illustrates a top-down plan view of an example of the pluralityof stacked waveguides of FIGS. 9A and 9B. As illustrated, the waveguides670, 680, 690, along with each waveguide's associated light distributingelement 730, 740, 750 and associated out-coupling optical element 800,810, 820, may be vertically aligned. However, as discussed herein, thein-coupling optical elements 700, 710, 720 are not vertically aligned;rather, the in-coupling optical elements are preferably non-overlapping(e.g., laterally spaced apart as seen in the top-down view). Asdiscussed further herein, this nonoverlapping spatial arrangementfacilitates the injection of light from different resources intodifferent waveguides on a one-to-one basis, thereby allowing a specificlight source to be uniquely coupled to a specific waveguide. In someembodiments, arrangements including nonoverlapping spatially-separatedin-coupling optical elements may be referred to as a shifted pupilsystem, and the in-coupling optical elements within these arrangementsmay correspond to sub pupils.

FIG. 9D illustrates an example of wearable display system 60 into whichthe various waveguides and related systems disclosed herein may beintegrated. In some embodiments, the display system 60 is the system 250of FIG. 6, with FIG. 6 schematically showing some parts of that system60 in greater detail. For example, the waveguide assembly 260 of FIG. 6may be part of the display 70.

With continued reference to FIG. 9D, the display system 60 includes adisplay 70, and various mechanical and electronic modules and systems tosupport the functioning of that display 70. The display 70 may becoupled to a frame 80, which is wearable by a display system user orviewer 90 and which is configured to position the display 70 in front ofthe eyes of the user 90. The display 70 may be considered eyewear insome embodiments. In some embodiments, a speaker 100 is coupled to theframe 80 and configured to be positioned adjacent the ear canal of theuser 90 (in some embodiments, another speaker, not shown, may optionallybe positioned adjacent the other ear canal of the user to providestereo/shapeable sound control). The display system 60 may also includeone or more microphones 110 or other devices to detect sound. In someembodiments, the microphone is configured to allow the user to provideinputs or commands to the system 60 (e.g., the selection of voice menucommands, natural language questions, etc.), and/or may allow audiocommunication with other persons (e.g., with other users of similardisplay systems. The microphone may further be configured as aperipheral sensor to collect audio data (e.g., sounds from the userand/or environment). In some embodiments, the display system may alsoinclude a peripheral sensor 120 a, which may be separate from the frame80 and attached to the body of the user 90 (e.g., on the head, torso, anextremity, etc. of the user 90). The peripheral sensor 120 a may beconfigured to acquire data characterizing a physiological state of theuser 90 in some embodiments. For example, the sensor 120 a may be anelectrode.

With continued reference to FIG. 9D, the display 70 is operativelycoupled by communications link 130, such as by a wired lead or wirelessconnectivity, to a local data processing module 140 which may be mountedin a variety of configurations, such as fixedly attached to the frame80, fixedly attached to a helmet or hat worn by the user, embedded inheadphones, or otherwise removably attached to the user 90 (e.g., in abackpack-style configuration, in a belt-coupling style configuration).Similarly, the sensor 120 a may be operatively coupled by communicationslink 120 b, e.g., a wired lead or wireless connectivity, to the localprocessor and data module 140. The local processing and data module 140may comprise a hardware processor, as well as digital memory, such asnon-volatile memory (e.g., flash memory or hard disk drives), both ofwhich may be utilized to assist in the processing, caching, and storageof data. Optionally, the local processor and data module 140 may includeone or more central processing units (CPUs), graphics processing units(GPUs), dedicated processing hardware, and so on. The data may includedata a) captured from sensors (which may be, e.g., operatively coupledto the frame 80 or otherwise attached to the user 90), such as imagecapture devices (such as cameras), microphones, inertial measurementunits, accelerometers, compasses, GPS units, radio devices, gyros,and/or other sensors disclosed herein; and/or b) acquired and/orprocessed using remote processing module 150 and/or remote datarepository 160 (including data relating to virtual content), possiblyfor passage to the display 70 after such processing or retrieval. Thelocal processing and data module 140 may be operatively coupled bycommunication links 170, 180, such as via a wired or wirelesscommunication links, to the remote processing module 150 and remote datarepository 160 such that these remote modules 150, 160 are operativelycoupled to each other and available as resources to the local processingand data module 140. In some embodiments, the local processing and datamodule 140 may include one or more of the image capture devices,microphones, inertial measurement units, accelerometers, compasses, GPSunits, radio devices, and/or gyros. In some other embodiments, one ormore of these sensors may be attached to the frame 80, or may bestandalone structures that communicate with the local processing anddata module 140 by wired or wireless communication pathways.

With continued reference to FIG. 9D, in some embodiments, the remoteprocessing module 150 may comprise one or more processors configured toanalyze and process data and/or image information, for instanceincluding one or more central processing units (CPUs), graphicsprocessing units (GPUs), dedicated processing hardware, and so on. Insome embodiments, the remote data repository 160 may comprise a digitaldata storage facility, which may be available through the internet orother networking configuration in a “cloud” resource configuration. Insome embodiments, the remote data repository 160 may include one or moreremote servers, which provide information, e.g., information forgenerating augmented reality content, to the local processing and datamodule 140 and/or the remote processing module 150. In some embodiments,all data is stored and all computations are performed in the localprocessing and data module, allowing fully autonomous use from a remotemodule. Optionally, an outside system (e.g., a system of one or moreprocessors, one or more computers) that includes CPUs, GPUs, and so on,may perform at least a portion of processing (e.g., generating imageinformation, processing data) and provide information to, and receiveinformation from, modules 140, 150, 160, for instance via wireless orwired connections.

Enhanced Eye Pose Determination Techniques

A display system (e.g., display system 60, FIG. 9D) described herein maybe used to present augmented or virtual reality content (referred toherein as virtual content). To present virtual content, the displaysystem may monitor eye poses of a user's eyes. As described herein, aneye pose may indicate an orientation of the eye, which may be utilizedto identify various parameters, such as a particular axis (e.g., opticaland/or visual axis) of the eye. Described below are techniques that, insome embodiments, may be applied to increase a speed at which eye posemay be determined, while additionally reducing power requirements andenabling mechanical efficiencies.

As described above, determining an eye pose may be used for variouspurposes to improve the viewing experience, and functionality,associated with presentation of virtual content. For example, an eyepose may inform how the display system renders virtual content. In thisexample, the display system may place render cameras at a respectivecenter of the user's eyeballs, to provide the correct views of virtualcontent to present to the user. Additionally, the display system may userapid eye pose determinations to reduce accommodation-vergencemismatches. As described in FIGS. 4A-4D, vergence-accommodationmismatches may be present in display system comprising a limited numberof depth planes. Each of the depth planes may correspond to a particularrange of depths from the user. Each depth plane has associatedaccommodation cues, and there may be limited available accommodationcues corresponding to the limited number depth planes. In contrast,vergence cues may be updated via adjusting a dichoptic presentation ofvirtual content. Thus, accommodation cues throughout a depth range maybe the same while vergence cues may be adjusted throughout that depthrange. The accommodation cues to provide to the user may be selectedbased upon the data plane on which their eyes are verging.Determinations of verging that lag the actual pose of the eyes mayundesirably introduce accommodation-vergence mismatches by providingaccommodation cues which do not correspond to the present vergence point(and plane) of the eyes. By accurately determining eye pose in realtime, the display system may determine the depth plane on which the eyesare verging, thereby allowing the display system to provide theaccommodation cues for that depth plane, to maintainaccommodation-vergence mismatch at low levels.

Advantageously, using the techniques described herein, eye pose may bedetermined at a substantially higher frequency (e.g., 1 kHz, 10 kHz, andso on) as compared to some existing techniques. Additionally, thisdetermination may be effectuated using components which require lesspower than some existing techniques. For example, light (e.g., infraredor near infrared light) may be directed from a light source (e.g., adiode, such as a VCSEL) onto a user's eye. In some embodiments, thelight may be reflected off of a movable reflector having a diffractivegrating, with the diffractive grating providing a light pattern. In someother embodiments, the light pattern may be formed at the light source(e.g., using a diffractive grating provided on an output surface of thelight source). The moveable reflector may be rotated about one or moreaxes such that the reflected light scans (e.g., sweeps) across theuser's eye. In some embodiments, the light may scan across thehorizontal axis of the user's eyes, the horizontal axis extending fromthe center of one eye to the center of the other eye. As mentionedabove, in some embodiments, the moveable reflector may be rotated abouta single axis such that the reflected light scans (e.g., sweeps) acrossthe user's eye in one dimension. For example, in at least some of theseembodiments, the moveable reflector may be configured and/or controlledsuch that the position of the reflected light pattern varies temporallyin a single, first dimension (e.g., across the horizontal axis of theuser's eye), while the light pattern itself exhibits spatial variance ina second, different dimension (e.g., across the vertical axis of theuser's eye). It is also to be understood that, in these embodiments, themoveable reflector may not be configured to rotate about more than oneaxis, or the moveable reflector may be configured to rotate about two ormore axes, but controlled in a manner so as to rotate about only one ofthe axes. It is also to be understood that, in these embodiments, thelight pattern itself may exhibit spatial variance in both the first andsecond dimensions. While the particular axis described herein is ahorizontal axis, in some other embodiments the light may be scannedacross a vertical axis of the user's eye.

Light reflected by the eye during this scan may be measured by athreshold number of light detectors (e.g., photodiodes) positioned aboutthe display system. For example, the light intensity of the reflectedlight may be measured. Light intensity patterns, corresponding to thedetected light intensity over time, as the light sweeps across the eye,may be determined. In some embodiments, the light intensity patterns maybe formed based on electrical current generated by each light detector.As described herein, non-uniformities in the eye may cause lightintensity patterns that are unique for different eye poses, and eye posemay thus be determined based on analysis of these light intensitypatterns. For example, the light intensity patterns may be matched withexpected patterns for different poses.

With reference now to FIG. 10A, a system and technique for determiningthe eye pose of a user is illustrated in a plan view. In the illustratedexample, a user's eyes 1002A, 1002B are represented. The user may be auser of a display system, such as display system 60 (FIG. 9D), and maybe viewing virtual content presented via the display system. Thus, theillustrated system may be understood to be part of the display system60. For example, the light source 1302, movable reflector 1006, andlight detectors 1014 may be attached to the frame 80 of the displaysystem 60. The frame 80 and the remainder of the display system 60,however, are not shown for ease of illustration and discussion. Inaddition, while a system for detecting the orientation of the eye 1002Ais illustrated, it will be appreciated that a similar system may beprovided for the eye 1002B and may determine the orientation of the eye1002B as discussed herein for the eye 1002A.

To determine the eye pose of the eye 1002A, an eye illumination system1003 may be configured to direct light 1010 onto the eye 1002A and toscan the light 1010 across the eye 1002A. In some embodiments, the eyeillumination system 1003 includes a light source 1302 which directs thelight 1004 onto a moveable reflector 1006, which reflects that lightonto the eye 1002A. In some embodiments, the moveable reflector 1006 maybe a microelectromechanical systems (MEMS) mirror. As mentioned above,in some embodiments, the moveable reflector 1006 may be aone-dimensional MEMS scanning mirror. In some embodiments, the lightsource 1302 may be a diode that emits light. As an example, avertical-cavity surface-emitting laser (VCSEL) may be used to output thelight 1004. In some embodiments, other diodes, other lasers, includingother sources of coherent light, and so on, may be used.

In some embodiments, the reflective surface of the movable reflector1006 may include a diffractive grating 1008. The light 1004 may bereflected by a diffractive grating 1008 on the moveable reflector 1006,such that a light pattern 1010 is formed. In some embodiments, the light1004 may be polychromatic light (e.g., infrared and/or near infraredlight). Different wavelengths (or colors) of light forming thepolychromatic light may be diffracted in different directions, therebycreating the pattern 1010. In the example of FIG. 10A, the light pattern1010 comprises two portions 1010A, 1010B which propagate in differentdirections away from the movable reflector 1006.

In some embodiments, the incident light 1004 may be monochromatic light(e.g., infrared or near infrared light). The two portions 1010A, 1010Bmay be formed using an appropriately configured diffractive grating(e.g., the diffractive grating may contain multiple sections havingdifferent orientations, sizes, geometries, etc. to achieve diffractionin the desired direction).

In this elevational view, these two portions 1010A, 1010B areillustrated as being projected towards the eye 1002A from the moveablereflector 1006. It will be appreciated, however, that the portions1010A, 1010B may be configured such that they form a light of light, orrow of light spots, spanning the eye 1002A in a vertical direction whenincident on the eye 1002A. For example, the portions 1010A, 1010B mayextend from a lower portion of the eye 1002A to an upper portion of theeye 1002A. A different perspective of this light pattern is illustratedin FIG. 10B, and will be described in more detail below.

With continued reference to FIG. 10A, the moveable reflector 1006 may becontrolled by the display system to move and cause the light pattern1010 to sweep along a horizontal axis across the eye 1002A. For example,and with respect to FIG. 10A, the light pattern 1010 may scan from aleft portion of the eye 1002A to a right portion of the eye 1002A. Insome embodiments, the light pattern 1010 may scan across an entirety ofthe sclera of the eye 1002A and across the iris and pupil, from one sideof the eye to another side of the eye. In some embodiments, the breadthof the scan may be more limited. For example, in some embodiments, thedisplays system may be configured to scan the light pattern 1010 acrossan entirety of the iris of the eye 1002A but less than the entirety ofthe expanse of the eye along the axis across which the sweep proceeds.The moveable reflector 1006 may be adjusted such that it rotates aboutone or more axes. As mentioned above, in some embodiments, the moveablereflector 1006 may be adjusted such that it rotates about a single axis.It will be appreciated that this rotation may adjust an angle at whichthe light 1004 is incident upon the diffractive grating 1008, therebychanging the direction that light is reflected to the eye 1002A andchanging the ultimate position that the light is incident on the eye1002A. Thus, the light pattern 1010 may be swept across the eye 1002A bymovement of the reflector 1006.

As illustrated, light detectors 1014 may receive reflected light 1012.It will be appreciated that the reflected light 1012 is the portion ofthe light 1010A, 1010B that is incident on and reflected from the eye1002A to the light detectors 1014. The reflected light 1012 may bereceived by the light reflectors 1014 while the moveable reflector 1006is causing the light pattern 1010 to sweep across a horizontal axis ofthe eye 1002A. It will be appreciated that different physiologicalfeatures of the eye 1002A may reflect light differently. For example,the cornea 1016 may protrude out of the remainder of the eye to reflectlight in different directions than other parts of the eye. In addition,different parts of the eye may have different reflectivity. For example,the sclera (the “white” of the eye) may be understood to reflect morelight than the iris, which may reflect more light than the pupil. Asanother example, different parts of the eye may be associated withdiffuse or specular reflections. The sclera, as an example, may causediffuse reflections such that a resulting light intensity pattern, forexample illustrated in FIG. 10B, may include light intensity peaks thatmore gradually increase, or decrease, in intensity and reach lowermaximum intensity values than specular reflections. In contrast,specular reflections may be associated with a ‘glint’ and result in asharp increase, or decrease, in intensity. Differentiating betweendiffuse light reflections and specular reflections may enabledifferentiation between reflections caused by portions of the eye, suchas sclera, iris, and pupil (providing diffuse reflections) fromreflections associated with “glint”, which may be used for identifyingeyeball/cornea curvature. Thus, the reflected light 1012 may vary inintensity during the scan, with the variations in intensity resultingfrom the eye features that the light 1010A, 1010B is incident. Dependingon the orientation of the eye, these variations may be expected to occurat different points during the scan (e.g., at different times). Thepattern of light intensity provided by the reflected light 1012 may thusrepresent a signature representative of a particular eye pose of the eye1002A.

The light detectors 1014 may convert the reflected light 1012 intoelectrical current. The display system may store information identifyingthe electrical current (or values derived from the current) as plottedagainst time or a position of the moveable reflector 1006 or incidentlight 1010A, 1010B, or may simply have certain electrical current values(or values derived from the electrical current) associated withparticular times and/or positions (or values derived from particulartimes and/or positions). Such a plot or sequence of values may bereferred to herein as a light intensity pattern. An example lightintensity pattern is illustrated in FIG. 10B. Preferably, multiple lightintensity patterns derived from light detectors at different locationsare utilized to increase the accuracy of the ultimate determination ofeye pose (or other eye parameters, as discussed herein).

With reference again to FIG. 10A, the illustrated example may include aplurality of light detectors 1014, which are schematically representedas a single block. However, it will be appreciated that the lightdetectors 1014 may be located at different positions in the displaysystem. For example, the system may include a plurality of lightdetectors arranged in a linear array, or at the corners of variousshapes (e.g., four light detectors positioned in a rectangularconfiguration about the eye 1002A of the user).

Preferably, the light detectors are positioned in front of the eye 1002Asuch that they receive reflected light 1012 during scanning. An exampleof such a configuration is illustrated in FIG. 11. It will beappreciated that the light intensity pattern of FIG. 10B is an exampleof a single light intensity pattern detected using a single lightdetector 1014. Each of the illustrated light detectors 1104A-1104D mayhave different light intensity patterns due being differentlypositioned, causing them to receive light 1012 reflected in differentdirections.

Each of the light detectors may thus generate a light intensity patternassociated with scanning the light pattern 1010 across the eye 1002A,e.g., across the horizontal axis. As discussed herein, the lightintensity patterns may be used by the display system to determine an eyepose for the eye 1002A. In some embodiments, subsequent to scanningacross the horizontal axis, the light pattern 1010 may be scanned in anopposite direction. Thus, two scans may be optionally be performed.These two scans may be used by the display system to determine an eyepose for the eye 1002A. In some embodiments, the moveable reflector 1006may generally cause the light pattern 1010 to scan in an oppositedirection only when determining a subsequent eye pose. Thus, an eye posefor the eye 1002A may be determined based on a single scan of the eye1002A in a direction across a horizontal axis (e.g., left to right). Asubsequent eye pose for the eye 1002A may then be determined based onscanning in an opposite direction along the horizontal axis (e.g., rightto left). Thus, the moveable reflector may not need to reset for eachscan to a same position which causes scanning from a same initialposition along a same horizontal direction. In this way, allowing scansto occur in opposite directions may increase a speed at which eyetracking may occur. For example, eye tracking speed may be doubled ascompared to requiring a scan in a same direction for each eye posedetermination.

The display system may then analyze the light intensity patterns todetermine the eye pose for the eye 1002A. For example, the positions ofthe light detectors 1014 and moveable reflector 1006 may be known to thedisplay system (e.g., via initial calibration). As another example, thepositions of the light detectors 1014 may be the same as light detectorsused to generate information usable to determine eye pose. As an exampleof determining the eye pose, each light intensity pattern may representa signature pattern associated with an orientation of the eye 1002A.Thus, an aggregation of these light intensity patterns may be used todetermine a specific eye pose with high accuracy.

In some embodiments, a machine learning model may be generated whichoutputs information identifying an eye pose based on an input of athreshold number of light intensity patterns. In this example, themachine learning model may have been trained based on a same, orsimilar, placement of the light detectors and moveable reflector. Forexample, light intensity patterns corresponding to known eye poses mayhave been generated using a similar placement of light detectors andmoveable reflector within a display system. In this example, the machinelearning model may then have been trained. As another example, lightintensity patterns along with information identifying placement of thelight detectors and moveable reflector (e.g., relative to an eye) mayhave been used as training information. In some embodiments, traininginformation may additionally indicate positions of light sources and/ormoveable reflectors.

In some embodiments, the display system may store informationidentifying light intensity patterns for each of a plurality of eyeposes. Thus, the display system may determine measures of similaritybetween the measured light intensity patterns from the light detectors1014 and the stored light intensity patterns. These measures ofsimilarity may include measuring similarity in peaks, valleys, slopes,curve-fitting techniques, and so on.

As an example, a light intensity pattern measured by a particular lightdetector may include different peaks and valleys. These peaks andvalleys may correspond to respective times or moveable reflector 1006positions at which the two portions 1010A, 1010B of the light pattern1010 reflect from the eye 1002A. Thus, there may be an “alpha” 1010Apeak at a particular time or moveable reflector 1006 position.Additionally, there may be a “beta” 1010B peak at a subsequent time ormoveable reflector 1006 position. The display system may determine eyepose based on these respective peaks. For example, the display systemmay identify the time or moveable reflector position for each of thepeaks. The display system may use these identified times or MEMSpositions for each of the photodiodes to match to a reference lightintensity pattern corresponding to a known eye pose.

With reference again to FIG. 10B, an example is illustrated of a lightintensity pattern 1022 associated with scanning the user's eye 1002Awith light pattern 1010. As described in FIG. 10A, the moveablereflector 1006 may form light pattern 1010 and direct that pattern ontothe user's eye 1002A with a diffractive grating 1008. Light detectors1014 may then receive reflected light 1012 from the eye 1002A. Asdescribed above, there may be a threshold number of light detectors 1014in different positions about the eye 1002A (e.g., 2, 3, 4, 6, or morelight detectors). Thus, each light detector may convert respectivereceived light into electrical current or a signal (e.g., a digital oranalog signal). This electrical current or signal may be measured andstored as a light intensity pattern 1022 by the display system.

In the illustrated example, the light pattern 1010 (e.g., a “V” pattern)is provided to the user's eye 1002A at a first location. As illustrated,the light pattern 1010 may extend along a vertical axis of the user'seye 1002A. Additionally, the light pattern 1010 may include an “alpha”portion 1010A which is angled opposite to that of a “beta” portion1010B. Thus, the portions 1010A, 1010B may be projected on differentportions of the user's eye 1002A at any given time during the scan.These two portions 1010A, 1010B may be used to inform an eye pose of theeye 1002A, as described below. In some embodiments, to differentiate thedifferent reflected light signals provided by each portion 1010A, 1010B,the portions may each be formed by light of different colors (fromincident polychromatic light, as discussed herein). In some otherembodiments, the different portions 1010A, 1010B may be formed by lightof the same color, and may be generated at different times byilluminating different parts of the moveable reflector 1006, which mayhave different diffractive gratings in those different parts. Generatingthe portions 1010A, 1010B at different times allows the differentsignals provided by the portions 1010A, 1010B to be differentiatedtemporally. In some other embodiments, the portions 1010A, 1010B may beformed by light of the same color and may be scanned simultaneouslyacross the eye.

With continued reference to FIG. 10b , at an initial time (e.g., timeto), the moveable reflector 1006 may be at an extremity of its range ofrotation. For example, the moveable reflector 1006 may be causing thelight pattern 1010 to be at a left-most, or right-most, position on theeye 1002A. In the illustrated example, the initial time corresponds tothe light pattern 1010 being projected onto a left-most portion of theeye 1002A. Light reflected from the eye 1002A may be measured at thisposition. An example of such an initial measurement 1024A is reflectedin the light intensity pattern 1022 in FIG. 10B. The light pattern 1010may be continuously, or discretely, moved across the eye 1002A by themoveable reflector 1006.

At a subsequent time 1020C, and thus a different moveable reflector 1006position, the light pattern 1010 may be moved as illustrated in FIG.10B. In this position of the moveable reflector 1006, the “alpha”portion 1010A of the light pattern 1010 has reached an extremity of theeye's 1002A pupil (e.g., a right-most portion). As illustrated in thelight intensity pattern 1022, the corresponding light detectorassociated with pattern 1022 is positioned such that at the subsequenttime 1020C, a peak 1024C (caused by a glint of the eye) is representedin the light intensity pattern 1022. In contrast, a valley 1024B isincluded in the light intensity pattern 1022 at an earlier time. Thisvalley 1024B may represent, for example, the moveable reflector 1006causing the “alpha” portion 1010A to reach an opposite extremity of theeye's 1002A pupil (e.g., a left-most portion). For this moveablereflector 1006 position corresponding to valley 1024B, the correspondinglight detector associated with pattern 1022 may have limited visibilityof reflected light and/or the light reflected to the light detector maybe reflected from a part of the eye with low reflectivity. Thus, avalley 1024B may be represented in the light intensity pattern 1022.

The light intensity pattern 1022 illustrates another peak 1024D at afurther time (e.g., at a further adjustment of the moveable reflector1006). The peak 1024D may correspond to a “glint” (e.g., a specularreflection), at the same location having the glint causing the peak1024C. This example peak 1024D may be generated based on the trailing“beta” portion 1010B of the light pattern 1010. For example, thecorresponding light detector associated with pattern 1022 may havesubstantially maximum visibility of light reflected from the “beta”portion 1010B at this further time. As a non-limiting example, this peak1024D may have been generated as the “beta” portion 1010B passes anextremity of the eye's 1002A pupil. This extremity may be the sameextremity providing the glint causing the peak of the “alpha” portion1010A. In this example, peak 1024D may correspond to the “beta” portion1010B passing the extremity and peak 1024C may correspond to the “alpha”portion 1010A passing the same extremity.

With continued reference to FIG. 10b , a processing device 1026 mayreceive the light intensity pattern 1022 and use the pattern 1022 todetermine an eye pose for the eye 1002A. The processing device 1026 may,in some embodiments, represent, or be included in, the local data andprocessing module 140 described above. The processing device 1026 mayoptionally obtain information identifying a direction associated with ascan of the light pattern 1010. For example, the resulting lightintensity pattern 1022 may be based on whether the light pattern 1010moves in a particular direction along the horizontal axis. As describedabove, with respect to FIG. 10A, the MEMS mirror 1006 may adjust tocause the light pattern 1010 to move along a first direction for a firsteye pose. The MEMS mirror 1006 may then rotate in an opposite directionto cause the light pattern 1010 to move along an opposite scan directionfor a second, subsequently determined, eye pose. In this way, the MEMSmirror 1006 may increase eye tracking speed as compared to requiringscanning along a same direction.

The processing device 1026 may obtain light intensity patterns from aplurality of light detectors. For example, where there are four lightdetectors, there may be at least four light intensity patternsassociated with a same scan of the eye 1002A. Each of these lightintensity patterns may include a unique pattern corresponding to theamount of reflected light incident on the associated light detectors.For example, a peak 1024C and a valley 1024B corresponding to the“alpha” portion 1010A may be positioned at different times or moveablereflector positions in different light intensity patterns. Thus, theprocessing device 1026 may use these light intensity patterns toidentify an accurate eye pose for the eye 1002A.

Due to the high speed at which a MEMS mirror 1006 may be adjusted, andthe limited information included in a light intensity pattern 1022, theprocessing device 1026 may rapidly determine an eye pose. In embodimentsin which a machine learning model is used, the processing device 1026may optionally compute a forward pass of a neural network. The neuralnetwork may optionally comprise one or more dense (e.g.,fully-connected) layers. For example, values corresponding to electricalcurrent and associated time or moveable reflector position may beprovided to the neural network. The neural network may optionallycomprise one or more convolutional layers which leverage the time-seriesnature of the light intensity patterns. These neural networks may havebeen previously trained. For example, training data may comprise knowneye poses and corresponding light intensity patterns. In this example,the positions of the moveable reflector 1006 and photodiodes mayoptionally be the same as, or similar to, the positions as used togenerate light intensity pattern 1022. Other machine learning models maybe used and fall within the scope of the disclosure herein. For example,a support vector machine may be used.

In some embodiments, the processing device 1026 may access storedinformation identifying known light intensity patterns and associatedeye poses. The processing device 1026 may then correlate the measuredlight intensity patterns (e.g., light intensity pattern 1022) with thestored information. The peaks (e.g., peak 1024C) and valleys (e.g.,valley 1024B) in the measured light intensity patterns may be correlatedwith peaks and valleys in the stored information. As described above,the moveable reflector 1006 may optionally scan across the eye 1002Aalong a first direction or a second, opposite, direction. Thus, theprocessing device 1026 may optionally reverse (e.g., reflect), orotherwise apply a linear transform to, the stored light intensitypatterns or measured light intensity patterns depending on a directionof the scan.

For example, the processing device 1026 may access stored lightintensity patterns for a particular light detector of the lightdetectors 1014. In this example, the processing device 1026 may identifya particular stored light intensity pattern which is closest to that ofa measured light intensity pattern for the particular light detector.While such a particular stored light intensity pattern may be identifiedbased on a multitude of different metrics, in some embodiments, theprocessing device 1026 may identify a particular light intensity patternwith similar positions of peaks and valleys. With respect to the lightintensity pattern 1022, the processing device 1026 may identify a storedlight intensity pattern which has peaks 1024C-1024D and valleys 1024B atsimilar times and/or similar moveable reflector 1006 positions.

Using a threshold number of these light intensity patterns 1022, theprocessing device 1026 may thus determine the eye pose of the eye 1002Awith high accuracy. As will be described further below, in someembodiments the processing device 1026 may use the light intensitypatterns to determine interfaces between physiological features of theeye 1002A. For example, an iris-to-pupil interface may be determined bythe processing device 1026.

With reference again to FIG. 11, as discussed above, an example isillustrated of the positions of light detectors 1104A-1104D within adisplay system 1102 for determining eye pose. The light detectors1104A-1104D may be, for example, photodiodes, phototransistors,photoresistors, or a combination thereof. The example representation isillustrated from a perspective of a user facing the display system 1102.For ease of reference, a user's eye 1002A is illustrated within theperspective. A plurality of light detectors 1104A-1104D are positionedabout the user's eye 1002A. As mentioned herein, in some embodiments,light detectors 1104A-1104D may be attached to a frame of the displaysystem 1102. For example, each of light detectors 1104A-1104D may beattached to a different portion of the frame surrounding an eyepiece. Inother embodiments, light detectors 1104A-1104D may be attached to and/orembedded in a layer of material positioned adjacent to the eyepiece(e.g., a protective cover for the eyepiece) or the eyepiece itself.Light may be directed and scanned across the eye 1002A as describedabove. For example, a light pattern may be created using a diffractivegrating positioned on, or otherwise adjustable by, a moveable reflector(e.g., a MEMS mirror).

Due to the different positions of the light detectors 1104A-110D, as thelight pattern is scanned across the eye, each light detector willreceive varying irradiance. In this way, each light detector maygenerate a distinct electrical current pattern. In some embodiments, thelight detectors may generate a digital or analog signal associated withthe received irradiance. For a given eye pose, each light detector willcreate a light intensity pattern which may represent a signatureassociated with the eye pose. As described above, with respect to FIGS.10A-10B, measured light intensity patterns may thus be used to rapidlyidentify an eye pose.

The illustration includes four light detectors 1104A-1104D positionedequidistant apart in a rectangular pattern. However, it should beappreciated that different positions may be used. For example, lightdetectors 1104A-1104B may be positioned closer together. As describedabove, the display system 1102 may determine eye pose based on a machinelearning model or stored information identifying known light intensitypatterns. This information may be generated based on a similarlyconfigured display system 1102. Thus, others positions of the lightdetectors 1104A-1104D may be used. For example, any positions for whichthe light detectors are able to receive reflected light may be used. Inaddition, the number of light detectors may total numbers other thanfour, as discussed herein. The machine learning model or storedinformation may be generated according to a particular configuration oflight detectors. If the display system 1102 also uses this sameconfiguration, then the display system 1102 may identify eye pose basedon the machine learning model or stored information.

With reference now to FIG. 12, an example is illustrated of a flowchartof a process 1200 for determining an eye pose of a user's eye. Forconvenience, the process 1200 will be described as being performed by adisplay system having one or more processors (e.g., the display system60, FIG. 9D).

At block 1202, the display system causes projection of a light patternvia a moveable reflector (e.g., a MEMS mirror). As illustrated in FIG.10A, the display system may output light using a light source (e.g., aVCSEL). This outputted light may be provided to a moveable reflector,which may optionally have a diffractive grating on its reflectivesurface. The diffractive grating may cause a light pattern to beprovided onto the user's eye. In some other embodiments, the moveablereflector is a specular reflector and the pattern may be formed upstreamof the moveable reflector, e.g., at the output of the light source.

At block 1204, the display system adjusts the moveable reflector to scanthe light pattern across the user's eye. The moveable reflector may bein a first position, such that the light pattern is projected at a firstportion of the user's eye. For example, the light pattern may beprojected at a left-most portion of the user's eye. The display systemmay then cause adjustment of the moveable reflector to cause the lightpattern to be projected along an axis. As described above, the axis maybe a horizontal axis. The light pattern may additionally extend across avertical portion of the user's eye. Additionally, the light pattern mayoptionally have a “V” shape formed by substantially continuous lines oflight as illustrated in FIG. 10B.

In some embodiments, the light pattern may have a shape different fromthat of a “V” shape formed by substantially continuous lines of light.For example, and as illustrated in and will be discussed furtherregarding FIG. 15, a light pattern may comprise spots or dots instead oflines which form two portions (e.g., the “alpha” portion and “beta”portion as described above). As another example, and as illustrated inand will be discussed further regarding FIG. 16, a light pattern mayencode an optical function. The optical function may increase light conediffusion or decrease a spot size to better differentiate signalsreceived by light detectors.

Optionally, the display system may initially scan the user's eye to findan interpupillary distance (IPD). The light projector may then bemodulated so it illuminates only the IPD region during the scan. Forexample, the IPD region, and all margin required to project light onto auser's eye in any eye orientation, may be used. In this way, displaysystem power may be reduced as certain users may have smaller IPDregions as compared to other users. Thus, the display system may conformthe scan to each user.

With continued reference to FIG. 12, at block 1206, the display systemobtains light intensity patterns from a threshold number of lightdetectors (e.g., photodiodes). As the moveable reflector causes thelight pattern to be scanned across the user's eye, the light detectorsmay generate corresponding electrical current or a detector signal. Thiselectrical current or detector signal may be represented as lightintensity patterns as describe above.

At block 1208, the display system determines eye pose based on theobtained light intensity patterns. As described in FIG. 10B, the displaysystem may use machine learning techniques to assign an eye pose to thelight intensity patterns. The display system may also determine measuresof similarity between the obtained light intensity patterns and knownlight intensity patterns. In some embodiments, the known light intensitypatterns may be stored as tabular data in which electrical current ismapped against time or moveable reflector position. In some embodiments,the known light intensity patterns may be stored as informationgenerated from analyzing the known light intensity patterns. Forexample, peaks, valleys, slopes, and so on, for the light pattern may bestored. In this example, and with respect to a “V” pattern, peaks andvalleys for an “alpha” and “beta” portion may be stored along withcorresponding positions of the moveable mirror.

In some embodiments, and as will be described further in FIGS. 18A-18D,the display system may determine an interface between differentphysiological portions of the eye. For example, the light intensitypatterns may include information indicative of such interfaces. As alight pattern is scanned across an interface, there may be acorresponding change in electrical current or signal generated by one ormore light detectors. An example interface may include an interfacebetween an iris and pupil. The display system may identify this exampleinterface based on differences in light absorption and reflectivitybetween the iris and pupil. For example, there may be greater lightabsorption and lower reflectivity in the pupil. In this example,resulting light intensity patterns may reflect a drop in electricalcurrent or signal when the light pattern traverses from the iris to thepupil.

With respect to an iris/pupil interface, the display system maydetermine a size and/or position of the pupil. For example, the displaysystem may determine a left-most interface and a right-most interface asrepresented in one or more light intensity patterns. The display systemmay then determine a size of the pupil based on a difference between theleft-most interface and right-most interface. This determination may bebased on the moveable reflector. For example, the display system mayidentify a distance from the left-most interface to the right-mostinterface along a horizontal axis based on a speed of rotation of themoveable reflector.

Example Eye Poses

FIGS. 13A-13C illustrate a light pattern being scanned across a firsteye pose of an eye. Similarly, FIGS. 14A-14C illustrate a light patternbeing scanned across a second eye pose of an eye. As discussed herein,these different eye poses will cause different light intensity patternsto be generated.

FIGS. 13A-13C illustrate an example of a light pattern 1010 beingprojected onto and scanned across a user's eye 1002A. In the illustratedexamples, the light source 1302 (e.g., a VCSEL diode) is projectinglight 1004 on the moveable reflector 1006, which may optionally have adiffractive grating 1008. The resulting light pattern 1010 thenpropagates to the eye 1002A. As illustrated, a portion of the light ofthe light pattern is then reflected off the eye 1002A as reflected light1012. As described above, light detectors (not shown) may be positionedabout the eye 1002A to receive the reflected light 1012.

FIGS. 13A-13C thus illustrate the light pattern 1010 being scannedacross the user's eye 1002A by adjusting the position of the moveablereflector 1006 (e.g., by rotating the moveable reflector 1006). It willbe appreciated that the reflected light 1012 is reflected in differentdirections depending on the position of the moveable reflector 1006.Thus, the light detectors positioned about the eye 1002A may eachgenerate a unique light intensity pattern. In this way, a display systemmay determine a specific eye pose corresponding to the eye poseillustrated in FIGS. 13A-13C.

For example, FIG. 13A illustrates the moveable reflector 1006 at aninitial position. At this initial position, the light pattern 1010 isdirected onto a corresponding initial position of the eye 1002A. Forthis eye pose, the initial position corresponds to a left portion of theeye 1002A. The reflected light 1012 for this initial position isillustrated as being reflected towards the left of the eye 1002A. Thisreflected light 1012 may be received by light detectors and electricalcurrent or signal may be correspondingly generated.

In FIG. 13B, the moveable reflector 1006 has scanned the light pattern1010 to a substantially central portion of the eye 1002A. In thisexample, the reflected light 1012 is being reflected towards both a leftand right of the eye 1002A. Light detectors may, in some embodiments, bepositioned about the eye 1002A (e.g., as illustrated in FIG. 11). Thus,light detectors positioned to the right of the eye 1002A may receiveadditional light as compared to light received in FIG. 13A.

In FIG. 13C, the moveable reflector 1006 has scanned the light pattern1010 to a right portion of the eye 1002A. This right portion maycorrespond to a final position of the moveable reflector 1006. For thisfinal position, reflected light 1012 is being reflected towards theright of the eye 1002A. Thus, the moveable reflector 1006 may scan thelight pattern 1010 via adjusting from the initial position to the finalposition. In some embodiments, the moveable reflector 1006 may scan thelight pattern 1010 by rotating about one or more axes. As mentionedherein, in some embodiments, the moveable reflector 1006 may scan thelight pattern 1010 by rotating about a single axis. An amount ofrotation may be based on physiological features of the eye 1002A. Forexample, the physiological features may include the sclera, cornea,pupil, and so on, and the amount of rotation may be based on acorresponding size (e.g., a length along a horizontal axis) of thefeature.

Subsequently, the display system may obtain light intensity patternsreflecting the light pattern 1010 being scanned from the initialposition to the final position. As described herein, these lightintensity patterns may be used to determine the eye pose illustrated inFIGS. 13A-13C.

FIGS. 14A-14C illustrate another example of a light pattern 1010 beingprojected onto and scanned across a user's eye 1002A, with the user'seye 1002A in a different pose than the eye shown in FIGS. 13A-13C. Inthe illustrated eye pose, the center of the eye 1002A is angled towardsthe right of the figure.

In FIG. 14A, the moveable reflector 1006 is at an initial position. Forthis eye pose, the light pattern 1010 is being provided to a leftportion of the eye. Since the illustrated eye pose is angled to theright as compared to the eye pose illustrated in FIGS. 13A-13C, thelight pattern 1010 is being provided to a different portion of the eye1002A. Thus, the reflected light 1012 is being reflected differentlyfrom the reflected light illustrated in FIG. 13A. Light detectorspositioned about the eye 1002A will thus generate a different measure ofelectrical current or signal.

In FIG. 14B, the moveable reflector 1006 has adjusted to cause the lightpattern 1010 to be scanned further across the eye 1002A along ahorizontal axis. For this example eye pose, the light pattern 1010 iscloser to a cornea of the eye 1002A. In contrast, the eye poseillustrated in FIG. 13B represents the eye 1002A looking straight ahead.Thus, in FIG. 13B the light pattern 1010 is being provided to asubstantially central portion of the eye 1002A. In FIG. 14C, themoveable reflector 1006 has adjusted to a final position. Asillustrated, the light pattern 1010 has been substantially scannedacross the cornea of the eye 1002A.

It will be appreciated that the light pattern 1010 has been scannedacross a different portion of the eye 1002A as compared to the eyeillustrated in FIGS. 13A-13C. Thus, resulting light intensity patternswill be unique as compared to the light intensity patterns resultingfrom the scan illustrated in FIGS. 13A-13C. For some eye poses, thelight pattern 1010 may be scanned across a substantially similar portionof the eye 1002A. For example, the light pattern 1010 may scan a similarportion of an eye looking straight forward and an eye looking down.However, these eyes will be in a different orientation such thatphysiological features of the eye will be in different orientations. Forexample, a cornea will be in a different orientation. Thus, thereflected light 1012 will result in generation of unique light intensitypatterns. In this way, the display system may determine eye pose basedon these light intensity patterns.

Example Light Patterns

FIG. 15 illustrates an example of a light pattern 1502 for scanningacross the user's eye. In this example, the light pattern 1502 createdby a diffractive grating 1008 is comprised of spots or dots of light,rather a continuous line of light. The light pattern 1502 may thusrepresent a pattern displacement which may be projected onto a user'seyes during adjustment of a moveable reflector (e.g., reflector 1006,FIG. 10). In some embodiments, multiple diffractive gratings withdifferent pitches may be etched to superimpose different diffractionpatterns, and thus create a “line” or points close enough to appear as aline.

FIG. 16 illustrates another example of a light pattern 1602 for scanningacross the user's eye. In some embodiments, the light pattern 1602 mayinclude multiple rows 1604, 1606, 1608 of light, which may be formed bydifferent lines of light or spots of light forming individual rows. Asillustrated, the rows 1604, 1606, 1608 may each define angles of lessthan 90° relative to the horizontal axis of the eye. To differentiatethe reflected light signals provided by each of the rows 1604, 1606,1608, the light forming the rows of light may have different properties.For example, light forming different ones of the rows 1604, 1606, 1608may have different colors or wavelengths, different polarizations (e.g.,where polarization sensitive light detectors are used), etc.

In some other embodiments, light forming different rows 1604, 1606, 1608may have different associated optical functions. As an example, theoptical function may increase light cone diffusion (e.g., may providebeams of diverging light). As another example, the optical function maydecrease a spot size (e.g., provide converging beams of light), whichmay be advantageous for providing a high signal to noise ratio for alight detector. As yet another example, a row may be formed by beams ofcollimated light. In some embodiments, the desired levels ofconvergence, divergence, or collimation may be provided by a holographicmaterial (e.g., surface or volume HOE) on the moveable reflector whichprovides both diffraction to formed the desired row pattern and a lensfunction (e.g., a collimation, focusing, or diverging lens function).

Two Light Sources

In some embodiments, two light sources (e.g., two VCSELs) may be used todetermine an eye pose of an eye. Each light source may output light withdifferent properties (e.g., different wavelengths or colors). Withrespect to the example of a “V” pattern, a first light source may beused to form a first portion (e.g., the “alpha” portion 1010A) and asecond light source may be used to form a second portion (e.g., the“beta” portion 1010B) of a light pattern. Using two lights sources mayprovide example advantages, such as reducing cross-talk. For example,there may be no cross-talk between the “alpha” portion and the “beta”portion. As another example, the scan time may be reduced. For example,the moveable reflector (e.g., MEMS mirror 1006) may be required toperform less adjustment (e.g., rotation about one or more axes) to scana user's eye.

FIG. 17A illustrates an example of a light pattern 1010 projected onto auser's eye using two light sources. In the left most portion of theillustration, the light pattern has the “alpha” portion 1010A of thelight pattern 1010 being formed by the first light source. For example,the “beta” portion 1010B is not being projected by the second lightsource. A plurality of light detectors may thus measure reflected lightwhile the “alpha” portion 1010A is being projected. Subsequently, andwith respect to the right-most portion of the illustration, the “beta”portion 1010B is being projected onto the user's eye. In contrast, the“alpha” portion 1010A is not being directed onto the user's eye. Theplurality of light detectors may thus measure reflected light while the“beta” portion 1010B is being directed onto the user's eye. In this way,cross-talk between these portions may be reduced or eliminated.

The display system may optionally generate two light intensity patternsfor each light detector, one for the “alpha” portion 1010A and one forthe “beta” portion 1010B. The display system may, as an example, storeinformation identifying times and/or MEMS mirror positions at whicheither the “alpha” portion 1010A or “beta” portion 1010B were beingprojected. In some embodiments, the display system may generate a singlelight intensity pattern which is representative of both the “alpha”portion 1010A and the “beta” portion 1010B and the portions 1010A, 1010Bmay optionally be scanned simultaneously across the eye.

FIG. 17B illustrates an example block diagram illustrating using twolights sources 1702A, 1702B. In the illustrated example, light isprovided to the moveable reflector 1006, which may optionally have adiffractive grating 1008 as discussed herein. In some embodiments, themoveable reflector 1006 may include a holographic element for generatingthe desired line of light (e.g., the hologram may be a multiplexedhologram, including one hologram selective for one wavelength for line“alpha” and another hologram selective for the wavelengths of light forline “beta”). In some other embodiments, the moveable reflector 1006 isa specular reflector and the desired pattern is formed at the lightsources 1702A, 1702B. A combiner 1704 may be used to direct light fromthe light sources 1702A, 1702B to the moveable reflector 1006.

Another implementation may include having two areas on the moveablereflector 1006. For each of the areas there may be a specificdiffraction grating, with each of the light sources being configured toilluminate one of the areas. Thus, different lines (e.g., “alpha”portion and “beta” portion) may be created. An example of such adiffractive grating with multiple diffraction zones is illustrated inFIG. 17C. Each diffraction zone may comprise differently configureddiffraction gratings. For example, the diffraction gratings of thediffraction zones may have different physical parameters, includingdifferent periodicities and/or different sizes (e.g. heights and/orwidths) for the individual structures (e.g., laterally-extending linesof material) forming the gratings.

Determining Size and/or Position of Physiological Features

It will be appreciated that the light intensity patterns may containinformation that may be utilized to determine eye parameters other thanpose. For example, the display system may be configured to use the lightintensity patterns described herein to determine the sizes and/orpositions of physiological features of a user's eye. Examplephysiological features may include a sclera, an iris, a pupil, aninterface between the sclera and the iris, an interface between the irisand the pupil, and so on. The display system may determine size and/orposition as an alternative to, or in addition to, determining eye pose.

With respect to an interface between the iris and pupil, the displaysystem may determine its position based on a change in electricalcurrent or signal as represented in one or more light intensitypatterns. For example, the display system may identify a peak or valley(e.g., a change in derivative greater than a threshold). With respect toa pupil, the display system may determine its size based on identifyingthe boundaries of the pupil. The boundaries may, as an example,correspond to a left-most interface and a right-most interface betweenthe pupil and the iris.

FIG. 18A illustrates an example flowchart of a process 1800 fordetermining physiological information associated with an eye of a user.For convenience, the process 1800 will be described as being performedby a display system of one or more processors (e.g., display system 60).

At block 1802, and as described above with respect to block 1204 of FIG.12, the display system adjusts a moveable reflector to scan a lightpattern across the eye. At block 1804, the display system obtains lightintensity patterns from a threshold number of light detectors, similarto block 1206 of FIG. 12. As described herein, the display system mayobtain light intensity patterns which represent a measure of electricalcurrent or signal generated by respective light detectors. Each lightintensity pattern may map electrical current or signal to time and/orposition of the moveable reflector.

At block 1806, the display system determines a size and/or positionassociated with a physiological feature of the eye. As discussed herein,in some embodiments, machine learning and/or pattern matching may beutilized to determine the locations of physiological features orboundaries, and sizes may be calculated from these determined locations.

Reference will now be made to FIGS. 18B-18D, which illustrate an exampleof determining size and/or position information associated with one ormore physiological features.

FIG. 18B illustrates the light pattern 1010 being scanned across the eye1002A. In the illustrated example, the light pattern has a “V” shapewhich may include an “alpha” 1010 a portion and a “beta” portion 1010 b.The “V” shape is described in more detail above with respect to at leastFIGS. 10A-10B. An example light intensity pattern 1814 is illustrated,which indicates a measure of signal or current from a light detectorreceiving light reflected from the eye 1002A during the scan. Theexample light intensity pattern 1814 may be associated with one of aplurality of the light detectors positioned about the eye 1002A. Anexample of light detectors positioned about an eye is illustrated inFIG. 11.

At a time or moveable reflector position represented in FIG. 18B, the“alpha” portion 1010 a of the light pattern 1010 is swept over at aninterface, or boundary, 1812 between the sclera and the iris. As thelight passes from the highly reflective white sclera to the darker, lessreflective iris, this intersection 1812 may show a reduction inreflected light received by a light detector associated with the pattern1814. The reflected light may result from diffusive reflections of thelight pattern 1010, and the pattern 1814 may thus indicate a gradualreduction in intensity. The light intensity pattern 1814 thereforeindicates this interface 1812 as a reduction in signal with respect toportion 1816 of the light intensity pattern 1814.

The display system may use the techniques described herein, such as amachine learning model or stored information, to determine that thisreduction in signal corresponds to the physiological interface 1812between the sclera and iris. For example, the display system may use athreshold number of light intensity patterns to effectuate thedetermination. The display system may then determine a positionassociated with this interface 1812. For example, the display system mayidentify a time mapped to portion 1816. In this example, the displaysystem may determine the position based on a speed at which the moveablereflector adjusts. As another example, the display system may identify amoveable reflector position associated with portion 1816. Based oninformation identifying a position of the moveable reflector, thedisplay system may determine a location at which the light pattern 1010is incident and which is causing the portion 1816 of the light intensitypattern 1814.

FIG. 18C illustrates the light pattern 1010 being further scanned acrossthe eye 1002A. The “alpha” portion 1010 a, in this example, is sweptpass an intersection 1822 between the iris and the pupil. Similar to theabove, as the light passes from the more reflective iris to the darker,less reflective pupil, this this intersection may show a reduction inlight reaching the light detector associated with the light intensitypattern 1814. Thus, a reduction in signal is indicated at portion 1824of the light intensity pattern 1814. The display system may thusdetermine a position associated with this interface 1822 as describedabove.

FIG. 18D illustrates the light pattern 1010 being further scanned untilthe “alpha” portion 1010 a is scanned across another interface 1832between the pupil and the iris. This interface 1832 represents aright-most interface between the pupil and the iris. In contrast, theinterface 1822 described in FIG. 18C represents a left-most interfacebetween the pupil and the iris. Similar to the above, the display systemmay determine a position associated with this interface 1832. In theillustrated light intensity pattern 1814, however, a peak 1834 caused bya glint coincides with the interface 1832. It will be appreciated thatthe glint provides a large amount of reflected light (e.g., specularlyreflected light) when the light pattern 1010 is scanned across theinterface 1834, which may obscure the detection of the interface 1834using the illustrated light intensity pattern 1814. However, asdiscussed herein, multiple light detectors providing multiple lightintensity patterns are preferably utilized and at least some of theseother light detectors would be expected to register a difference inreflected light intensity due to changes in reflectivity at theinterface 1832. For example, these other light intensity patterns (notshown) may show the reverse of the portions 1824 and 1816 of the lightintensity pattern 1814 and may be utilized to determine the location ofthe interface 1832.

Based on the interface 1822 illustrated in FIG. 18C and the interface1832 illustrated in FIG. 18D, the display system may determine a sizeassociated with the pupil. For example, the size may represent a sizealong a horizontal axis. In this example, the size may thereforerepresent a length of the pupil along the horizontal axis, e.g., a widthor diameter of the pupil. The display system may additionally determinea position of the pupil. For example, the display system may calculate acentroid of the pupil (e.g., a midpoint of the pupil width) asdetermined based on interfaces 1822, 1832.

It will be appreciated that the interface or boundary between the irisand the sclera, and the size of the iris, may by determined as discussedabove for the interface between the iris and the pupil and the size ofthe pupil. For example, the locations of the left and right interfacesof the iris may be determined based on the detected reduction inreflected light and the reflected light level being higher than thelower reflected light level of the pupil.

While the description above identified that the display system maydetermine an interface (e.g., interface 1812) prior to completion of ascan, in some embodiments the display system may determine theinterfaces upon completion of the scan. For example, the display systemmay obtain light intensity patterns and determine size and/or positioninformation based on the light intensity patterns. In this example,machine learning techniques may be leveraged. For example, one or moremachine learning models may be trained to identify (e.g., label)physiological features based on light intensity patterns.

Estimating Eye Speed

In some embodiments, the display system may determine a velocity of auser's eye. For example, the display system may determine a speed ofrotation. The speed of rotation may be used for disparate purposes bythe display system, such as identifying the occurrence of a saccade orestimating an extent to which the eye will rotate during a saccade. Aswill be described, the display system may determine a speed of rotation(e.g., a saccadic velocity) based on comparing movement of one or morephysiological features or differences between successive eye poses.

The display system may determine a speed of rotation based on adifference in successively determined eye poses. For example, at a firsttime the display system may perform a scan of a user's eye. In thisexample, the display system may associate a first eye pose determinedbased on the scan with this first time. At a second time, the displaysystem may perform a subsequent scan of the user's eye. The displaysystem may then associate a second eye pose with this second time. Oneor more measures of a difference in eye pose between the first eye poseand second eye pose may be determined. An example measure may include anadjustment of an optical or visual axis between the first eye pose andsecond pose. The display system may then determine the speed of rotationusing the difference in the determined position of the optical or visualaxis and the difference in time between the first time and second time.

The display system may also determine a speed of rotation based onmovement of one or more physiological features. For example, at a firsttime the display system may determine a first position of aphysiological feature (e.g., an interface between an iris and pupil).Subsequently, at a second time the display system may determine a secondposition of the physiological feature. An extent to which thephysiological has feature moved, for example along one or more axes, maybe identified. The display system may then determine speed of rotationbased on the difference in the determined position of the physiologicalfeatures and a difference between the first time and second time.

A saccade may be understood to represent a rapid movement of an eyebetween two or more phases of fixation. During the occurrence of asaccade, a user may have reduced visibility between two fixations. Insome embodiments, the display system may adjust presentation of virtualcontent to leverage this reduced visibility. To identify the occurrenceof a saccade, the display system may determine whether a speed ofrotation of an eye exceeds a threshold. Due to the techniques describedherein, the display system may advantageously scan the eye at a ratehigh enough to detect saccades (e.g., 1 kHz, 10 kHz, and so on). Thus,the occurrence of a saccade may be determined. This determination may beutilized to influence depth-plane switching in a multi-depth planedisplay, as discussed in, e.g., US Patent Application Publication No.2017/0276948, published Sep. 28, 2017, the entirety of which isincorporated by reference herein.

Additionally, it will be understood that an extent to which an eye willrotate during a saccade may be based on an initial rotation speed(saccadic velocity) of the eye. For example, it will be understood thatthe initial saccadic velocity of an eye, the angle the eye is moving,and the final orientation of the eye after a saccade are correlated.Thus, the display system may estimate a final location at which the userwill fixate upon completion of the saccade, if the initial velocity anddirection are known.

It will be appreciated that different users may have differentassociated saccadic velocities. The display system may advantageouslyuse machine learning techniques to generate a model associated with aparticular user's saccadic velocity. For example, the display system mayidentify an initial speed and direction associated with a saccade. Inthis example, the display system may then identify an extent to whichthe eye rotated upon completion of the saccade (e.g., by constantlyscanning the eye and determining pose as described herein). Based onthis information, the display system may train, or otherwise update anexisting, machine learning model. As an example, the machine learningmodel may learn an accurate correlation between saccadic velocity,direction, and the end point of a particular user's eye.

Being able to estimate this end point may allow the final after-saccadepose to be determined. As discussed herein, the display system may usethis estimated pose in the presentation of virtual content to the user.In some embodiments, the estimated pose may be used to validate and/ordetermine a confidence level in the pose determined using thelight-scanning and light intensity pattern-based techniques discussedherein.

Other Embodiments

The various aspects, embodiments, implementations or features of thedescribed embodiments can be used separately or in any combination.Various aspects of the described embodiments can be implemented bysoftware, hardware or a combination of hardware and software. Thedescribed embodiments can also be embodied as computer readable code ona computer readable medium for controlling manufacturing operations oras computer readable code on a computer readable medium for controllinga manufacturing line. The computer readable medium is any data storagedevice that can store data, which can thereafter be read by a computersystem. Examples of the computer readable medium include read-onlymemory, random-access memory, CD-ROMs, HDDs, DVDs, magnetic tape, andoptical data storage devices. The computer readable medium can also bedistributed over network-coupled computer systems so that the computerreadable code is stored and executed in a distributed fashion.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the describedembodiments. However, it will be apparent to one skilled in the art thatthe specific details are not required in order to practice the describedembodiments. Thus, the foregoing descriptions of specific embodimentsare presented for purposes of illustration and description. They are notintended to be exhaustive or to limit the described embodiments to theprecise forms disclosed. It will be apparent to one of ordinary skill inthe art that many modifications and variations are possible in view ofthe above teachings.

It will also be appreciated that each of the processes, methods, andalgorithms described herein and/or depicted in the figures may beembodied in, and fully or partially automated by, code modules executedby one or more physical computing systems, hardware computer processors,application-specific circuitry, and/or electronic hardware configured toexecute specific and particular computer instructions. For example,computing systems may include general purpose computers (e.g., servers)programmed with specific computer instructions or special purposecomputers, special purpose circuitry, and so forth. A code module may becompiled and linked into an executable program, installed in a dynamiclink library, or may be written in an interpreted programming language.In some embodiments, particular operations and methods may be performedby circuitry that is specific to a given function.

Further, certain embodiments of the functionality of the presentdisclosure are sufficiently mathematically, computationally, ortechnically complex that application-specific hardware or one or morephysical computing devices (utilizing appropriate specialized executableinstructions) may be necessary to perform the functionality, forexample, due to the volume or complexity of the calculations involved orto provide results substantially in real-time. For example, a video mayinclude many frames, with each frame having millions of pixels, andspecifically programmed computer hardware is necessary to process thevideo data to provide a desired image processing task or application ina commercially reasonable amount of time.

Code modules or any type of data may be stored on any type ofnon-transitory computer-readable medium, such as physical computerstorage including hard drives, solid state memory, random access memory(RAM), read only memory (ROM), optical disc, volatile or non-volatilestorage, combinations of the same and/or the like. In some embodiments,the non-transitory computer-readable medium may be part of one or moreof the local processing and data module (140), the remote processingmodule (150), and remote data repository (160). The methods and modules(or data) may also be transmitted as generated data signals (e.g., aspart of a carrier wave or other analog or digital propagated signal) ona variety of computer-readable transmission mediums, includingwireless-based and wired/cable-based mediums, and may take a variety offorms (e.g., as part of a single or multiplexed analog signal, or asmultiple discrete digital packets or frames). The results of thedisclosed processes or process steps may be stored, persistently orotherwise, in any type of non-transitory, tangible computer storage ormay be communicated via a computer-readable transmission medium.

Any processes, blocks, states, steps, or functionalities in flowdiagrams described herein and/or depicted in the attached figures shouldbe understood as potentially representing code modules, segments, orportions of code which include one or more executable instructions forimplementing specific functions (e.g., logical or arithmetical) or stepsin the process. The various processes, blocks, states, steps, orfunctionalities may be combined, rearranged, added to, deleted from,modified, or otherwise changed from the illustrative examples providedherein. In some embodiments, additional or different computing systemsor code modules may perform some or all of the functionalities describedherein. The methods and processes described herein are also not limitedto any particular sequence, and the blocks, steps, or states relatingthereto may be performed in other sequences that are appropriate, forexample, in serial, in parallel, or in some other manner. Tasks orevents may be added to or removed from the disclosed exampleembodiments. Moreover, the separation of various system components inthe embodiments described herein is for illustrative purposes and shouldnot be understood as requiring such separation in all embodiments. Itshould be understood that the described program components, methods, andsystems may generally be integrated together in a single computerproduct or packaged into multiple computer products.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes may be made thereto withoutdeparting from the broader spirit and scope of the invention. Thespecification and drawings are, accordingly, to be regarded in anillustrative rather than restrictive sense. For example, whileadvantageously utilized with AR displays that provide images acrossmultiple depth planes, the augmented reality content disclosed hereinmay also be displayed by systems that provide images on a single depthplane.

Indeed, it will be appreciated that the systems and methods of thedisclosure each have several innovative aspects, no single one of whichis solely responsible or required for the desirable attributes disclosedherein. The various features and processes described above may be usedindependently of one another, or may be combined in various ways. Allpossible combinations and subcombinations are intended to fall withinthe scope of this disclosure.

Certain features that are described in this specification in the contextof separate embodiments also may be implemented in combination in asingle embodiment. Conversely, various features that are described inthe context of a single embodiment also may be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination may in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination. No single feature orgroup of features is necessary or indispensable to each and everyembodiment.

It will be appreciated that conditional language used herein, such as,among others, “can,” “could,” “might,” “may,” “e.g.,” and the like,unless specifically stated otherwise, or otherwise understood within thecontext as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or steps. Thus, such conditional language is notgenerally intended to imply that features, elements and/or steps are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or withoutauthor input or prompting, whether these features, elements and/or stepsare included or are to be performed in any particular embodiment. Theterms “comprising,” “including,” “having,” and the like are synonymousand are used inclusively, in an open-ended fashion, and do not excludeadditional elements, features, acts, operations, and so forth. Also, theterm “or” is used in its inclusive sense (and not in its exclusivesense) so that when used, for example, to connect a list of elements,the term “or” means one, some, or all of the elements in the list. Inaddition, the articles “a,” “an,” and “the” as used in this applicationand the appended claims are to be construed to mean “one or more” or “atleast one” unless specified otherwise. Similarly, while operations maybe depicted in the drawings in a particular order, it is to berecognized that such operations need not be performed in the particularorder shown or in sequential order, or that all illustrated operationsbe performed, to achieve desirable results. Further, the drawings mayschematically depict one more example processes in the form of aflowchart. However, other operations that are not depicted may beincorporated in the example methods and processes that are schematicallyillustrated. For example, one or more additional operations may beperformed before, after, simultaneously, or between any of theillustrated operations. Additionally, the operations may be rearrangedor reordered in other embodiments. In certain circumstances,multitasking and parallel processing may be advantageous. Moreover, theseparation of various system components in the embodiments describedabove should not be understood as requiring such separation in allembodiments, and it should be understood that the described programcomponents and systems may generally be integrated together in a singlesoftware product or packaged into multiple software products.Additionally, other embodiments are within the scope of the followingclaims. In some cases, the actions recited in the claims may beperformed in a different order and still achieve desirable results.

1.-84. (canceled)
 85. A display system configured to present virtualcontent to a user, the display system comprising: a light sourceconfigured to output light; a movable reflector configured to reflectthe outputted light to the eye of the user to scan a pattern formed ofthe light across the eye; a plurality of light detectors configured todetect reflections of the light scanned across the eye; and one or moreprocessors configured to perform operations comprising: causingadjustment of the orientation of the moveable reflector, such that thereflected light is scanned across the eye; obtaining, via the lightdetectors, respective light intensity patterns, wherein a lightintensity pattern represents light detector signals at different times,the light detector signals being obtained during scanning of thereflected light across the eye; and determining, based on the lightintensity patterns, an eye pose of the eye, the eye pose representing anorientation of the eye.
 86. The display system of claim 85, wherein themovable reflector comprises a diffractive grating, wherein thediffractive grating is configured to convert an incident beam of lightfrom the light source into a light pattern comprising multiple lines oflight spanning an area of the eye.
 87. The display system of claim 85,wherein the movable reflector comprises a plurality of diffractivegratings, each diffractive grating configured to form a different lightpattern for scanning across the eye.
 88. The display system of claim 85,wherein the light detectors are photodiodes, and wherein each lightintensity pattern represents a plot of electrical current versusposition information associated with a position of the movablereflector.
 89. The display system of claim 88, wherein the diffractivegrating is positioned on, or forms part of, a MEMS mirror, and whereinthe position information indicates an orientation of the MEMS mirror,the MEMS mirror being adjustable by the display system.
 90. The displaysystem of claim 85, wherein the light source is one of two light sourcesconfigured to output light to the movable reflector, wherein each of thelight sources is configured to form a respective portion of the patternof the light for scanning across the eye.
 91. The display system ofclaim 85, wherein the pattern of the light comprises a plurality ofsequential rows of light.
 92. The display system of claim 91, whereindifferent rows of light comprise beams of light having different amountsof divergence.
 93. The display system of claim 92, wherein a row oflight comprises converging beams of light, wherein an other of the rowsof light comprise collimated beams of light.
 94. The display system ofclaim 92, wherein a row of light comprises diverging beams of light. 95.The display system of claim 85, further comprising a waveguide, whereinthe waveguide is one of a stack of waveguides, wherein some waveguidesof the stack have out-coupling optical elements configured to outputlight with different amounts of wavefront divergence than out-couplingoptical element of other waveguides of the stack, wherein the differentamounts of wavefront divergence correspond to different depth planes.96. A method implemented by a display system of one or more processors,the display system being configured to present virtual content to a userbased, at least in part, on an eye pose of an eye of the user, whereinthe method comprises: adjusting a position of a light pattern directedonto the eye, such that the light pattern moves across the eye;obtaining a plurality of light intensity patterns, the light intensitypatterns representing light detector signals at different times, thelight detector signals obtained from respective light detectors duringadjustment of the position of the light pattern; and determining, basedon the light intensity patterns, the eye pose of the eye, the eye poserepresenting an orientation of the eye.
 97. The method of claim 96,wherein adjusting the position of the light pattern comprises moving amoveable mirror such that the light pattern is moved from a firstportion of the eye to a second portion of the eye along an axis.
 98. Themethod of claim 97, wherein the movable reflector comprises adiffractive grating, wherein the diffractive grating is configured toconvert an incident beam of light from the light source into a lightpattern comprising multiple beams of light.
 99. The method of claim 96,wherein determining eye pose comprises: applying a machine learningmodel via computing a forward pass of the light intensity patterns,wherein an output of the machine learning model indicates an eye pose.100. The method of claim 96, wherein determining eye pose comprises:accessing information identifying stored light intensity patterns, thestored light intensity patterns being associated with respective eyeposes; comparing the obtained light intensity patterns with the storedlight intensity patterns; and identifying the eye pose based on thecomparing.
 101. The method of claim 100, wherein comparing the obtainedlight intensity patterns with the stored light intensity patterns isbased on comparing positions of peaks and/or valleys in the lightintensity patterns.
 102. Non-transitory computer storage media storinginstructions that when executed by a display system of one or moreprocessors, cause the one or more processors to perform operationscomprising: adjusting a position of a light pattern directed onto an eyeof a user, such that the light pattern moves across the eye; obtaining aplurality of light intensity patterns, the light intensity patternsrepresenting light detector signals at different times, the lightdetector signals obtained from respective light detectors duringadjustment of the position of the light pattern; and determining, basedon the light intensity patterns, an eye pose of the eye, the eye poserepresenting an orientation of the eye.
 103. The computer storage mediaof claim 102, wherein the operations further comprise: causingprojection of the light pattern to the eye via a reflector having adiffractive grating.
 104. The computer storage media of claim 103,wherein an orientation of the diffractive grating is adjusted such thatthe light pattern is moved from a first portion of the eye to a secondportion of the eye.